Holders Manchester United, Villarreal, Bayern Munich and Arsenal are on brink of making the knockout stage should they avoid defeat in their respective matches on matchday five.

On the other hand, a handful of clubs vie for a UEFA Cup place ahead of the final round next month.

Group E

Top duo United and Villarreal lock horns at El Madrigal, knowing that a draw would be enough to grant both of them places in the last 16.

United will be without injured trio Dimitar Berbatov, Wes Brown and Gary Neville, but Cristiano Ronaldo should be fit to feature after training with the team on Monday. Goalkeeper Edwin Van der Sar is rested.

Joseba Llorente and Nihat Kahveci are out injured for Villarreal, who had a miserable weekend, losing 3-0 at home to struggling Valladolid. Injured defender Diego Godin is also unavailable.

In the other group game, Celtic visit Aalborg as both sides virtually have no chance of qualifying, but the contest remains alive for the UEFA Cup spot.

Group F

Bayern are firm favorites to beat minnows Steaua Bucharest at Allianz Arena. The Romanian champions, who have one point, are now 12 games without a win in all competitions.

Defender Martin Demichelis is likely to be rested, while striker Lukas Podolski, who pronounced his desire to leave the club in January, returns from a thigh injury.

In Florence, Fiorentina host leaders Lyon, who need a point from the game to book their knockout place.

Marco Donadel, Pablo Osvaldo and Stevan Jovetic are major doubts for Viola, whereas French international Anthony Reveillere joins long-term absentees Francois Clerc and Mathieu Bodmer on the Lyon sidelines.

Group G

Arsenal are seeking redemption following a turbulent domestic form in late, even though they will be in a comfortable position when they take on Dinamo Kiev at Emirates.

The Gunners have a host of key players on the injury list, including Emmanuel Adebayor, Samir Nasri, Theo Walcott, Bacary Sagna, Abou Diaby, Emmanuel Eboue and Kolo Toure.

However, newly-assigned captain Cesc Fabregas returns to the starting lineup after missing the 3-0 defeat at Manchester City through suspension. Midfielder Milos Ninkovic is out injured for Dynamo.

In Istanbul, Fenerbahce are in a must-win situation when they entertain Porto at Sukru Saracoglu. The Turkish giants are yet to win a game in this season's competition.

Defender Diego Lugano and midfielder Selcuk Sahin are suspended for Fener, the same goes to Porto star man Lucho Gonzalez, who saw red in Kiev three weeks ago.

Group H

Leaders Juventus are one of two teams to have already guaranteed a place in the next round. The Bianconeri visit UEFA Cup champions Zenit Petersburg; the Russians need nothing less than a win.

Juve are without long-term casualties Gianluigi Buffon, David Trezeguet, Mauro Camoranesi, Cristiano Zanetti, Christian Poulsen, Dario Knezevic, , and Tiago. Zenit miss Nicolas Lombaerts and Lee Ho.

In Borisov, Belarusian champions BATE are pushing for a UEFA Cup spot as they host Spanish titans Real Madrid, who got back to winning ways with a scrappy 1-0 win over Recreativo at the weekend.

Real coach Bernd Schuster is facing a selection dilemma, due to his side's long injury list, which includes high-profile names like Ruud Van Nistelrooy, Fabio Cannavaro and Arjen Robben.

Moreover, the Primera Liga champions are sweating over the fitness of Wesley Sneijder and Gonzalo Higuain, who has been Real's main source of goals since they lost Van Nistelrooy to injury.