The Champions League group stages get underway Tuesday with a set of mouth-watering match-ups and major tests for European powerhouses. Every Champions League game is brought to you live in HD this season across the FOX family of networks and DirecTV, with real-time in-game coverage on Twitter @FOXSoccerTrax and FOXSoccerTrax2 and on-line at

Tuesday's biggest games include a Group E clash between Chelsea and Bayer Leverkusen (live, FOX Soccer Plus, 2 p.m. ET); two Group F tussles featuring troubled teams as Arsenal travel to Dortmund (live, FOX Soccer Net, 2 p.m. ET) and Olympique Marseille visit Olympiakos; and an intriguing early meeting in Group H between defending champs Barcelona and hopefuls AC Milan (live, FOX Soccer 2 p.m. ET). Also in action are Europa League champs Porto, hosting Ukrainian power Shakhtar in Group G.

Wednesday will see some of the biggest names in the sport in action as Manchester United, Real Madrid, Manchester City, Lyon and Inter Milan all make their bows. Barcelona remain the team to beat, even if their shock draw on the weekend against Real Sociedad raised some eyebrows. Could the endless grind finally be catching up with a team that, after all, also forms the nucleus of the Spanish national side? Maybe -- but don't count on it.

Barcelona still have, on paper, the best team in club football, with a dizzying passing and attacking game that features Lionel Messi, David Villa, Xavi, Andres Iniesta and new signing Cesc Fabregas. Mind you, Cesc -- the onetime Arsenal captain -- won't start, showing how much depth this team truly has. Carlos Puyol is expected to return to head up the defense after recovering from knee surgery; missing will be Alexis Sanchez (hamstring) and Gerard Pique (calf).

AC Milan have fewer choices: Zlatan Ibrahimovic was itching for a shot at his former club, but a lingering groin injury meant he didn't even travel to Nou Camp. Robinho is also out (groin) meaning Milan is expected to start Alexandre Pato up top. Milan rallied from a 2-0 deficit to draw against Lazio on the weekend, and showed real grit. Mark van Bommel will face off against Xavi for the first time since the 2010 World Cup final; Kevin-Prince Boateng is questionable; Gennaro Gattuso is suspended and suffered an eye injury Friday in any case.

Both Barca and Milan are expected to march through their group with ease; Plzen and BATE, who face each other Tuesday, merely appear to be make-weights. The most compelling match may well be Arsenal's clash with Borussia Dortmund. In days past, this might have been a blockbuster; now, with both teams looking very fragile, this contest could be as much a test of psychology as ability.

Arsenal won on Saturday but in very unconvincing fashion, pipping newly promoted Swansea 1-0 thanks to a dreadful error by the Swansea goalkeeper, Michael Vorm. The fact that the result was treated as something of a triumph illustrates how grim the feelings are around the Emirates these days. New signings Mikel Arteta and Per Mertesacker both impressed in their debuts, but there was no mistaking the fact that Arsenal lack confidence as a squad; gone was the ability to put lesser opponents to the sword as they once could. The losses of Jack Wilshere, Aaron Ramsey and Thomas Vermaelen to injury have further depleted a squad that will also be missing manager Arsene Wenger, suspended after violating a touchline ban.

Dortmund have issues of their own. The reigning champs ran away with the Bundesliga crown last season, displaying a ruthlessness we usually associate with the likes of Bayern Munich. But that well-earned and deserved confidence has taken a series of hits, the latest coming when they were firmly outplayed by Hertha Berlin on the weekend in a shock 2-1 loss that ended a long unbeaten home spell. Dortmund have just two wins in five games but will be able to field Mario Goetze -- who Arsenal tried and failed to sign during the window -- after his league suspension. Goetze will lead the attack out of the midfield with American-youth international Neven Subotic holding down Dortmund's back line. Keep an eye on last year's breakout star, Japan's Shinji Kagawa; Lucas Barrios is out injured.

Chelsea are definite contenders but come in to their game looking like a third-place team in their own league. It is not that they are weak; it is that the Manchester's look so much better than all other comers that even a very capable Stamford Bridge side is being put into the shade. That said, cracks are already showing under new manager Andre Villas-Boas: his $80 million misfire Fernando Torres has shown no signs of breaking out of his death spiral and made matters worse by apparently criticizing his teammates in an interview on the weekend...on his own website. He claim he was "mis-translated" so we'll help: don't expect to see Torres start Tuesday.

Chelsea showed some of the old cut and thrust against a Sunderland side in free fall Saturday, with an exceptional goal from Daniel Sturridge. But the performances of Frank Lampard, Nicolas Anelka and the absence of Didier Drogba (concussion) remains worrying.

Bayer Leverkusen have a lot of promise and are riding a hot streak off a 4-1 thumping of Augsburg Friday night. Renato Augusto has been so brilliant he may well keep one time Chelsea man Michael Ballack pinned to the bench against his old club. Andre Schurrle has been deadly up top. Leverkusen will miss a couple of key players: first choice keeper Rene Adler is out as is Swiss midfielder Tranquillo Barnetta (both knee.)

Olympique Marseille have a difficult task in Greece after another lousy weekend. Booed off the field at halftime, OM would go on to lose 1-0 to Rennes in a disjointed performance playing out against a backdrop of locker room unrest. Andre-Pierre Gignac exploded last week, revealing he had been set for a deadline-day move to Fulham, only to find that OM wanted to deal him to Sunderland. The result? No deal, and one unhappy striker. Missing for OM against what is expected to be a full-strength Olympiakos side that includes former Lyon and Villa midfielder Jean Makoun are Andrew Ayew (groin), Stephane Mbia (broken foot) and Mathieu Valbuena (hamstring, suffered this weekend).

Finally, FC Porto face Shakhtar Donetsk in what casual observers might confuse for a Brazilian league match. The teams field a combined 16 Brazilian nationals and both are enjoying huge success: Porto are riding a remarkable 39 game league unbeaten streak; Shakhtar are league leaders after nine games in Ukraine.

This is not exactly the same Porto that took what we all used to call the UEFA Cup last year. For starters, Andre Villas-Boas is now helming Chelsea; for another, Porto dealt last year's top scorer Radamel Falcao to Atletico during the window. They still have lots of weapons, with Premier League targets Hulk and Danilo topping a list that includes Cristian Rodriguez and Joao Moutinho. Rolando and Fredy Guarin are suspended for the game; new signing Steve Defour, late of Liege, is expected to get a look.

Shakhtar have the 1-2-3 punch of Jadson, Luiz Adriano and Willian alongside Douglas Costa and Fernandinho. Dontesk are missing the injured Oleksandr Kucher and Vyacheslav Shevchuk but got back the hugely influential full back Dmytro Chygrinsky on the weekend; he feeds out to Razvan Rat wide and cleans up in front of Tomas Hubschman. The ageless Darijo Srna holds the armband and the right flank.