Status: Spanish champions, European champions
THE RECORD: The reigning kings of the Champions League took their time to join the ranks of the continent's elite as they did not lift their first European title until their 1992 triumph against Sampdoria at Wembley, yet they have made up for lost time by winning the ultimate prize in club football three times in the last five years.
TACTICIAN: Pep Guardiola
The Barca boss is fortunate to be working with a squad so sublimely talented that he merely needs to add the icing atop what is a deliciously appetising cake.
It has been suggested that any tactician would succeed at the helm of this Barca side, yet the dignity and calm professionalism this former Barca midfielder has shown since he took up the role in 2008 has provided the perfect backdrop to the brilliance at his fingertips. "Being European champions is a title we embrace and we want to do all we can to defend our trophy this season," Guardiola says.
THE GAMEPLAN: The summer signings of Cesc Fabregas and Alexis Sanchez have given the unstoppable Barca juggernaut even more attacking potency, with coach Guardiola switching from his winning 4-3-3 formula and experimenting with a 3-4-3 set-up. Defending, it seems, is becoming increasingly less significant for free-scoring Barca.
Barca's unrelenting desire to retrieve the ball on the rare occasions they do not have it has been a key factor in their dominance of European game, with the magic they produce when the ball is under their control never ceasing to delight and enchant.
MAIN MAN: Lionel Messi
There can only be one candidate to fill this position for Barcelona and it has to be the brilliant Messi, an attacking genius who already deserves be placed alongside the all-time greats of the game.
His majestic performance in last season's Champions League final against Manchester United confirmed beyond any doubt that he is in a league of his own in the modern era and his hunger for more shows no sign of waning. "Winning the Champions League at Wembley was a special moment for all of Barcelona, but this team will not be happy to settle for what we have," he says. "We want more and more."
BIG SIGNING: Cesc Fabregas
Fabregas' return to his first club finally came to pass this summer as, after much wrangling, Arsenal were forced to reluctantly hand their skipper back to Barcelona in a deal worth around £35 million.
The expectation was that Fabregas would eventually replace the majestic Xavi in the Barca midfield and that he may not be a first-choice pick this season, yet the new formation means there is room for Fabregas to add even more majesty to Guardiola's line-up straight away. He started scoring goals from the moment he put a Barca shirt on his back once more.
RISING STAR: Thiago
Barca fans enjoy seeing a graduate of their celebrated youth academy make the leap into their star-studded first-team and Thiago looks set to be given his chance to do just that as the champions defend their Champions League crown.
With Thiago's buy-out clause in his Barca contract reported to be a staggering €90 million, it is clear that the Catalan giants expect this classy 20-year-old to flourish into a true star. Born in Italy as the son of Brazilian World Cup-winner Mazinho, he was raised in Spain and has committed his international future to his adopted nation.
THE X FACTOR: Alexis Sanchez
Barca hardly needed any additional magic, yet the £25 million summer capture of Sanchez provided a thrilling injection of invention.
This Chile international may not be a first pick in the initial stages of this season's Champions League, but he offers coach Guardiola an option to give star names a rest if required. That could be a crucial factor when the knockout stages kick in next February.
FLAW IN THE MAKE-UP: Guardiola has been fortunate to have Messi, Iniesta and Xavi fit and available on a consistent basis throughout his time as Barca boss, but we have yet to discover whether his side would continue to thrive amid an injury crisis.
Messi, in particular, has bailed his side out of trouble time again in recent years and it would be impossible to fill the void he would leave should he be sidelined for a sustained period. That said, Barca have enough class oozing from their fringe players and celebrated youth academy to plug holes when they arise.
WHAT THEY SAY: "Barcelona are a fantastic team and there is no denying that they are right up there with the best of all time," Manchester United boss Sir Alex Ferguson says - and he is a man normally reluctant to pour praise on his chief rivals. "The challenge for everyone in Europe is to try and improve to get close to them because they mesmerise you with their passing and punish you with their finishing. Sometimes you have to accept you are beaten by the better team and that was certainly the case for us in last season's Champions League final."
VERDICT: If they perform at their best and stay injury-free, no one can stop them.
Status: Italian champions
THE RECORD: Italy's most successful club in Champions League history, Milan have reigned supreme over the continent's finest on seven occasions and contributed to some of the most iconic moments in the history of this competition.
Their fall from grace in recent Champions League campaigns has been somewhat alarming and the challenge for Massimiliano Allegri and his team is to build on their domestic success last season against the cream of European football.
ACTICIAN: Massimiliano Allegri
The Milan chief achieved his first goal after taking over as Milan boss in the summer of 2010 as he knocked local rivals Inter off their perch by wresting the Serie A title from their grasp. Now comes the challenge of getting this famous old club back to winning ways in the Champions League.
"I have told the players that they can reach the Champions League final this season," Allegri says. "This is a realistic target because we are a team with the history and belief to intimidate any opponent. I like the additions we have made to the squad and we are stronger than last season for sure."
THE GAMEPLAN: The attacking riches Allegri has at his disposal will give him selection headaches aplenty if injuries do not play a part in the Milan story this season, with Zlatan Ibrahimovic, Antonio Cassano, Alexandre Pato, Stephan El Shaarawy and Robinho all in the shake-up for starting spots.
His 4-3-1-2 formation ensures defensive solidity is at the heart of his gameplan, with the game changers in the attacking third charged with firing the bullets to see off the opposition. Tottenham exposed Milan's midfield as one-dimensional in last season's Champions League, so improvements are required and a summer of big change in the Milan dressing room heralded fresh hope.
MAIN MAN: Zlatan Ibrahimovic
This big Swede has divided opinions down the years, with his supporters hailing him as the ultimate target man in European football and the doubters believing he is an over-rated slayer of modest opposition who goes missing when the going gets tough.
He did little to dispel the myth that he is only effective in a dominant team as he failed to make his mark in the Champions League second-round tie against Tottenham last season, yet this maverick performer will be determined to prove his critics wrong as he returns to Europe's elite competition this season.
BIG SIGNINGS: Taye Taiwo and Philippe Mexes
Milan tried to reshape their defensive line with some cut-price signings during the summer transfer window and the capture of Taiwo and Mexes should give them some fresh impetus at the back.
Nigerian Taiwo arrived from Marseille, while Frenchman Mexes comes via Roma and is recovering from a knee injury he picked up at the back end of last season. With his signature secured on a free transfer, it was a sound piece of business for Milan.
RISING STAR: Stephan El Shaarawy
Signed from Genoa in June, the belief is that this teenager has the potential to take the Champions League by storm this season.
Blessed with blistering pace and plenty of trickery on the ball, the attacking midfielder who has been capped by Italy at junior levels inherited his exotic name from his Egyptian father. "It has always been my dream to play for Milan as they were the team I followed when I was growing up," he says. "Kaka is my idol and I would love to play like him for a successful Milan team.
THE X FACTOR: Alberto Aquilani
The mere mention of Aquilani's name gets Liverpool fans hot under the collar as they are still furious that ex-boss Rafael Benitez wasted around £20 million of the club's money on this injury-prone misfit who has barely kicked a ball for the Reds since his expensive arrival in 2009.
After his loan spell at Juventus last season failed to lead to a permanent transfer, Liverpool boss Kenny Dalglish was relieved to find another taker for this former Roma star as Milan took him on loan for the season. He is a midfielder with plenty to prove in this season's Champions League.
FLAW IN THE MAKE-UP: Milan were exposed as one-dimensional by Tottenham in last season's Champions League, with Spurs boss Harry Redknapp dampening down their ambitions as his side secured a famous 1-0 aggregate win in the second-round tie.
A midfield featuring ageing stars Clarence Seedorf, Mark van Bommel and Gennaro Gattuso may lack the pace to unsettle the better sides in Europe, meaning much will depend on the likes of Pato, El Shaarawy and Robinho to provide the magic spark required.
WHAT THEY SAY: "It will be interesting to see if Milan can be better this season because they were a long way short in the Champions League last time," club legend Ruud Gullit says. "I was disappointed with their performances against Tottenham last season and they have to convince us all that they have improved."
VERDICT: Barcelona aside, the group-stage draw has been kind to Milan, but they may struggle to make a splash in the knock-out stages.
Status: Belarusian champions
Nicknames: The Car Workers, Zholto-Sinie (Yellow-and-Blues)
THE RECORD: The only team from Belarus to qualify for the Champions League, BATE reached the promised land in 2008-09 and again this year.
Three years ago, they beat Valur of Iceland, Anderlecht and Levski Sofia en-route to the group stage, where, in a group featuring Juventus, Real Madrid and Zenit St Petersburg, they finished bottom with three points. However, it was not all doom and gloom as home and away draws with Juventus suggested they could compete at this level.
TACTICIAN: Viktor Goncharenko
It's little wonder that Goncharenko is regarded as one of the best up-and-coming team coaches in Eastern Europe. Not only has he led his club to three straight Belarus League titles (2008, 2009 and 2010), he has also transformed a once-anonymous provincial outfit into a credible force on the continental stage, qualifying BATE for the 2008-09 Champions League and for the second round of last season's Europa League.
A defender with BATE from 1998 to 2002, his career was ended prematurely by injury, staying on at the club to work with the juniors. He took over as first-team boss from Igor Kriushenko in November 2007 and, when he led BATE into the Champions League in the autumn of 2008, the then 31-year-old Goncharenko became the youngest coach in the history of the competition.
THE GAMEPLAN: Goncharenko usually employs a 4-2-3-1 system but may opt for a more defensive 4-5-1 in the Champions League. He is a man obsessed with the efficiency and togetherness of the team unit and has a three-point recipe for success: great organisation, superior fitness and tactical nous. They are sharp and intelligent on the counter-attack and very disciplined in the way the hold their shape.
To have any chance of holding their own, BATE must stand firm defensively and will be looking to twin-centre-backs Marko Simic and Egor Filipenko and midfield enforcers Dmitriy Baga and Edgar Olekhnovich to fight the good fight. High-profile new-boy Mateja Kezman can either lead the line or play in a more withdrawn attacking role.
MAIN MAN: Renan Bressan
This talented Brazilian-born attacking midfielder was the top scorer in the Belarus League last year with 15 goals, which was no mean feat for a player who does so much more than merely score goals.
The 22-year-old has been starring in Belarus for the past four seasons, first at FC Gomel, before BATE made their move for him last year. From Santa Catarina state in Brazil, he not only received a trophy when voted the Belarus Player of the Year for 2010 but also had his citizenship application rubber-stamped. Now there are rumours of top clubs tracking his progress.
BIG SIGNING: Mateja Kezman
Bidding for one last hurrah on the big stage, this veteran Serbia striker recently signed a contract with BATE until the end of the year and, if all goes well, there is the possibility of a longer-term deal.
Now 32, he was a prolific marksman in his younger years, piling up the goals for both Partizan Belgrade and PSV Eindhoven, but it all started to go horribly wrong for Kezman following a move in 2004 to Chelsea. He made next to no impact at Stamford Bridge and, from that moment on, he has largely flattered to deceive, particularly disappointing while at Paris Saint-Germain from 2008 to 2010. He had a temporary deal to play for Hong Kong outfit South China last season.
RISING STAR: Maksim Skavysh
One of six BATE players in the Belarus Under-21 side that finished third at this year's European Championships, this intelligent and mobile young front-man made his first-team debut for BATE back in 2007 and appeared in every one of his club's Champions League games in their 2008-09 effort.
Although only 21, Skavysh has already won three Belarus League titles (2008, 2009 and 2010), a domestic cup (2010) and two national Supercups (2010 and 2011). He's an ever-willing runner off the ball, creative and a decent finisher.
THE X FACTOR: Vitali Rodionov
An accomplished 27-year-old attacker who can both fly solo up top or play just off the main striker, Rodionov took time to settle after joining BATE from Torpedo Zhodino in 2006.
He came good a couple of years later, scoring 16 times in the Belarus League in the second half of the 2008-09 season. In 2009, he was loaned out to German Second Division for Freiburg and performed ably, only for the Black Forest club to surprisingly not take up the option to buy him.
FLAW IN THE MAKE-UP: BATE are essentially a very young and raw side, made up of products from their excellent academy. At the sharp end of Champions League competition, this naivety will be ruthlessly exposed.
They are much the weaker for the recent departure of midfielder Pavel Nekhaichik to Dinamo Moscow as he was outstanding at breaking late into the box. Meanwhile, the signing of Mateja Kezman is a real gamble as he is a fading force and could end up disrupting the tight-knit family at BATE.
WHAT THEY SAY: "Success for BATE will be third-place in their group," former BATE star Alexander Hleb says. "Barcelona and Milan are on another planet entirely, but my old team can beat the Czechs from Plzen. This European campaign is just one more step on the development road. There's so much they can learn from being in this fabulous group."
VERDICT: No chance of qualification for second round, but a win or two against Viktoria Plzen will be hailed as glory for BATE.
Since his appointment as Viktoria boss in 2008, Vrba has performed a string of minor miracles with the unfashionable west Bohemian club, steering them to victory in the Czech Cup in 2010 and to their first national championship title last season. His all-conquering success has led many in the local media to suggest it is only a matter of time before he takes charge of their Czech national side. A former professional in the old Czechoslovak League with Cheb and Banik Ostrava, this genial and modest 47-year-old coached Zilina to the Slovak League title in 2007 and also served as an assistant to Slovakia national team boss, Jan Kocian.
"This has been the best season year of my career," beamed the 36-year-old as Viktoria clinched the Czech championship spoils in May and no one could argue with him. Bought from Sparta Prague in 2007, his probing, prompting, perfectly-weighted passes and set-piece delivery were at the heart of the Plzen success story. Since starting out with Sparta Prague in the early 1990s, Horvath has gone on to play for Jablonec, Slavia Prague and Teplice in his homeland, as well as Turkish giants Galatasaray and Sporting in Lisbon.
A livewire little frontrunner or attacking midfielder recently signed on loan from the Hradec Kralove club, Pilar is widely-regarded as the golden boy of his generation. This 22-year-old left-footer likes to punch holes in defences with his speed and low centre of gravity and now he gets his chance to prove he can hurt the best in the Champions League. Pilar has settled in straight away at Viktoria, scoring from the off and becoming a instant hero for the Plzen faithful. He made his senior debut for the Czech Republic in June of this year in a Kirin Cup match against Peru.
This busy, technical and incisive right-sided midfielder has grown steadily in confidence and influence since joining Plzen from Sparta Prague in 2007. Offering industrious and dynamic bursts on his flank, accuracy with his crossing and his share of goals too, Petrzela is a game changer in the Czech league. Something of a late developer, he only won his first full cap for the Czech Republic at the not-so tender age of 27 and is now an established member of the Czech side pushing for qualification for Euro 2012. His former clubs include FK Drnovice, FC Slovacko and Jablonec.