Barcelona welcomes Ajax for historic first-ever competitive clash between the two soccer giants

A first-ever meeting of Barcelona and Ajax, two of European soccer's most famous names, tops the billing on Wednesday's Champions League card, while Jose Mourinho's Chelsea and last season's runner-up Borussia Dortmund are also in action.

Group E

Chelsea vs Basel: Jose Mourinho's quest to win the Champions League with Chelsea recommences with a home fixture against Swiss champion Basel at Stamford Bridge. These clubs met as recently as May, with Chelsea winning 5-2 on aggregate in the semifinals of the Europa League on its way to lifting the trophy with a final victory against Benfica in Amsterdam. However, it only dropped into that competition after being eliminated from the Champions League at the group stage. This season's draw is a kind one, however, and the London club will be confident of getting back on track after Saturday's Premier League loss at Everton, even if it must do without the suspended Ramires.

Schalke 04 vs Steaua Bucharest: After a troubled start to the campaign, Schalke's confidence has been lifted thanks to a run of three consecutive victories. The most recent of those was a 1-0 triumph away to Mainz in the Bundesliga on Saturday, secured thanks to Kevin-Prince Boateng's first goal for the club. Boateng returned to Germany after scoring twice for AC Milan in its playoff round win over PSV Eindhoven, although he is eligible to represent Schalke in the group stage and will have an important role to play for Jens Keller's side, which has been without Klaas-Jan Huntelaar recently due to a knee injury. Romanian champion Steaua, the 1986 European Cup winner, came through three qualifying rounds to return to the group stage for the first time since 2008-09.

Group F

Marseille vs Arsenal: Arsenal has injury problems, with Santi Cazorla joining the likes of Alex Oxlade-Chamberlain and Lukas Podolski on the sidelines, but the signing of Germany star Mesut Ozil has lifted the London club and he helped inspire it to a 3-1 win at Sunderland in the Premier League on Saturday. That was a fifth consecutive win for Arsene Wenger's side in all competitions ahead of its visit to familiar foe Marseille. The clubs met in the group stage of the same competition two years ago, with Arsenal winning 1-0 in the south of France before a goalless draw in London. Elie Baup's side, which needed a late goal to draw 1-1 at Toulouse in Ligue 1 on Saturday, is the outsider in a testing group.

Napoli vs Borussia Dortmund: Last season's Champions League runner-up kickoff its campaign with a trip to Naples, in what is a contender for the outstanding game of matchday one. Juergen Klopp's side is top of the Bundesliga having won all five matches so far, including a 6-2 trouncing of Hamburg on Saturday. Summer signings Pierre-Emerick Aubameyang and Henrikh Mkhitaryan were both on target in that game, and Dortmund could scarcely be in better shape ahead of this match at the Stadio San Paolo. Napoli, however, also boasts a perfect record in Serie A, with summer recruits Gonzalo Higuain and Jose Callejon netting in Saturday's 2-0 home win against Atalanta. It returns to the Champions League after a year's absence having lost to Chelsea in the last 16 two years ago. This time it is coached by a European specialist in Rafael Benitez, the mastermind of Liverpool's 2005 triumph and Chelsea's Europa League victory last season.

Group G

Atletico Madrid vs Zenit St Petersburg: Europa League winner twice in the past four seasons, Diego Simeone's side returns to Europe's leading club competition fresh from winning its opening four games in La Liga. The most recent of those was a 4-2 defeat of Almeria on Saturday, featuring goals by strike duo Diego Costa and David Villa. Brazilian frontman Costa will not be able to play in Wednesday's game at the Vicente Calderon stadiumdue to a suspension carried over from last season, though, and Atletico can expect a stern test from big-spending Zenit. The Russians will be eager to do better than last season, when they failed to make it beyond the group stage, and warmed up with a 2-0 win against Rostov on Saturday, which left them in second place in the Russian Premier League.

Austria Vienna vs Porto: Portuguese champion Porto begins its Group G campaign at the scene of one of its greatest triumphs, with its match against Austria Vienna being played at the Ernst-Happel Stadion. It was there that Porto won its first European Cup in 1987, Rabah Madjer's legendary backheeled effort helping it come from behind to beat Bayern Munich 2-1 in the final. Porto lost the likes of James Rodriguez and Joao Moutinho over the summer, and has a new coach this season in Paulo Fonseca, but it has proven adept at rebuilding quickly in the past and still boasts greater experience than its host, which is competing in the group stage for the first time. Nenad Bjelica's side came through two qualifying rounds to get here, but warmed up for this game by losing 3-2 at home to Groedig in the Austrian Bundesliga on Saturday.

Group H

Barcelona vs Ajax: Group H brings together four former winners of the trophy, and both Barcelona and Ajax have been European champions on four separate occasions. The links between Barca and Ajax are plentiful, notably thanks to Johan Cruyff, who starred as a player and a coach for both sides. Rinus Michels and Louis van Gaal also coached both sides, while former Ajax player Frank Rijkaard led the Catalans to Champions League glory in 2006. Remarkably, though, this will be the first-ever competitive meeting of the two clubs. While the Dutch champion will arrive at the Camp Nou led by Frank de Boer, who spent four years as a player at Barcelona, the match will be an entirely new experience for his opposite number in the dugout. Tata Martino, who's overseen four wins out of four so far in La Liga, has plenty of experience in South America's Copa Libertadores, but none of the Champions League.

AC Milan vs Celtic: Seven-time European champion Milan entertains 1967 winner Celtic in Italy in a repeat of a 2007 last-16 tie, which the Serie A club won 1-0 after extra-time thanks to a Kaka goal. The Brazilian has recently returned to the San Siro after four years with Real Madrid but will miss Wednesday's game due to injury. Milan needed two late goals to earn a 2-2 draw at Torino on Saturday and also had to come through a playoff against PSV Eindhoven to reach the group stage. Massimiliano Allegri's side will be very much the favorite to get the better of the Scottish champion, which needed to win three qualifying ties to get this far. All-conquering at home, Neil Lennon's Celtic was comfortably beaten by another Italian club, Juventus, in the last 16 of this competition last season.