German hopes Schalke 04 travel to Atletico Madrid on Wednesday, Aug. 27, holding a narrow 1-0 lead from the first leg but are still depleted by injuries. Peru striker Jefferson Farfan, Dutch midfielder Orlando Engelaar, goalkeeper Manuel Neuer and midfielder Jermain Jones are among those likely to be sidelined.

Schalke were boosted by a fighting 1-1 draw at Werder Bremen on Saturday and Dutch coach Fred Rutten will be aiming for a similar performance in Madrid.

Atletico are hoping for a win to enable them to return to the Champions League, after an absence of 11 years.

It is not clear if coach Javier Aguirre will risk Argentinean international Sergio Aguero from the start, after his return from Olympic duty in Beijing.

Instead, he might leave him on the bench and use him as his second-half ace-up-the-sleeve up front with Uruguayan Diego Forlan.

Spanish and Italian giants Barcelona and Juventus look well placed to advance after comfortable 4-0 wins at home two weeks ago.

Barcelona, who won the title in 2006, travel to Polish champions Wisla Krakow on Tuesday aiming to finish the job off after goals by Samuel Eto'o, Thierry Henry and Xavi Hernadez gave them a comfortable 4-0 first-leg win.

The Spanish club's new coach Josep Guardiola is likely to stick by the team which did so well in the first leg, which means continuing with Eto'o and Henry in attack -- and leaving Olympic gold medalist Lionel Messi on the bench.

Juventus are at Slovakia's Artmedia on Tuesday looking in little trouble on their return to European competition two years after being sent down to Serie B because of allegations of match-fixing and bribing officials.

Premiership hoping to dominate again

England also hopes to make have a quartet of teams again in the group stage, with Arsenal and Liverpool both holding home advantage on Wednesday.

However, five-time champions Liverpool will need to beat Standard Liege after they labored to a goalless draw in Belgium.

Captain Steven Gerrard was unavailable for that match with a thigh strain but has now recovered, scoring the last-minute winner in a 2-1 defeat of Middlesborough on Saturday.

New signing Robbie Keane is eager to be on the European stage in first season with the club after joining from Tottenham.

"We've got two wins out of two in the league and that's all you can ask for," he told the club's Web site. "Now we will look ahead to Wednesday's game against Liege and we know how important it is to make sure we get into the group stages."

Sami Hyypia is a doubt with a hamstring injury, while the involvement of Luca Leiva, Javier Mascherano and Ryan Babel depends on how they have recovered from their exertions at the Olympics.

Arsenal, the 2006 losing finalists, are well placed to advance after a 2-0 win at FC Twente but confidence was dented by a 1-0 defeat at London rivals Fulham on Saturday.

"The result is there and we have to cope with it," manager Arsene Wenger said after the match. "We have a big game on Wednesday night and we have to respond with a top class performance because what we did today was just not good enough."

Cesc Fabregas could be back following the hamstring problem that has prevented him playing so far this season. Philippe Senderos is very doubtful with a hamstring problem, while Abou Diaby, Tomas Rosicky and Eduardo are all out.

Mountains to climb for many hopefuls

Elsewhere on Wednesday, Olympiakos of Greece have a mountain to climb after they lost 3-0 at Anorthosis Famagusta, but former champions Marseille are 1-0 up for the visit of Norway's Brann Bergen, while Dynamo Kiev are strongly placed after winning 4-1 at Spartak Moscow.

Former European champions Steaua Bucharest entertain Turkey's Galatasaray after a 2-2 draw in the first leg, while fellow Istanbul club Fehnerbahce take on visiting Partizan Belgrade with the score also evenly poised at 2-2.