Several Champions League knockout stage regulars can take a step closer to the last 16 on Wednesday, with Barcelona, AC Milan and Chelsea all in strong positions coming into matchday three. Pep Guardiola's defending European champions entertain Viktoria Plzen at the Camp Nou in a Group H clash that has all the makings of a major mismatch. After losing 2-0 to Milan at the San Siro three weeks ago, the odds against Viktoria winning in Catalonia are as high as 66-1 with some bookmakers. Barca remain unbeaten this season, and stayed on top of La Liga following a comfortable 3-0 victory over Racing Santander on Saturday. Now Eric Abidal says the task for an injury-hit Barca -- Gerard Pique is the latest man on the treatment table -- is a simple one ahead of a double-header against the Czech outsiders. "There are six points at stake in these games. If we win them both, we will have ten points which will be enough to take us into the last 16," said the France full-back. Meanwhile, Milan will be looking for Antonio Cassano, Robinho and Zlatan Ibrahimovic to reproduce the form they showed in Saturday's 3-0 success against Palermo as they prepare to host BATE Borisov in the other Group H meeting at the San Siro. Chelsea defend their unbeaten record in Group E when they host Belgian champions Genk at Stamford Bridge. With all the focus on the two Manchester giants, the west London outfit have been making steady progress under Andre Villas-Boas, and have scored eight goals in winning their last two Premier League games. Fernando Torres has not featured in either of these games due to suspension, but the Spaniard is available again and Villas-Boas hinted at a return for the 27-year-old against a side who have been struggling for form in their domestic league. "If we don't decide on him, it will be a long time out of the game," he said. "But he has been keeping fit and training and played for Spain. It's just a decision we have to make, bearing in mind what we want for the team." Elsewhere in Group E, two former Champions League runners-up meet as Bayer Leverkusen entertain Valencia in Germany. Valencia were beaten finalists in 2000 and 2001, while Leverkusen lost to Real Madrid in Glasgow in 2002 but, a decade on, the chances of either side going as far again appear slim.However, Leverkusen captain Michael Ballack, the one survivor from the Factory Team's line-up in the 2002 final, is looking for the class of 2011 to follow in his footsteps. "There are many young players...with huge potential, who have been lying in wait for this, to be able to play on this stage of the Champions League, and now it's up to us, to each individual, to make the best of it," he told UEFA.com. Valencia's form so far this season -- just one defeat in all competitions -- proves that they will not be easy opponents, however. Neither Marseille nor Arsenal have found form easy to come by recently ahead of their meeting in France in Group F. Arsenal's troubles have been well-documented, although they do at least go to the Stade Velodrome boosted by Sunday's Premier League victory over Sunderland. Marseille have won two out of two in the group, and a win on Wednesday would see them take a huge stride towards the next stage, but just one win in ten Ligue 1 outings means confidence remains tender. "If we take four points (from the two meetings with OM) then we will qualify," said Gunners' boss Arsene Wenger. "They have had a similar run to us -- a disappointing start in the championship and they have done well in the Champions League. It is exactly the same." Olympiakos and Borussia Dortmund meet in Greece with both sides still chasing a first win in the group that would revitalise their hopes of progress. APOEL Nicosia are the only side still unbeaten in Group G, but they could be in for a tough time against Porto, while Shakhtar Donetsk and Zenit St Petersburg go head to head in Ukraine.