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It's no exaggeration to say confidence is in short supply at Schalke. Jens Keller's men are still without a win in 2014/15 and now have the unenviable task of facing one of the tournament favourites in their own back yard. That said, Sporting Lisbon and Slovenian club NK Maribor complete Group G, so whatever happens on the night shouldn't put too much of a downer on the Royal Blues' qualification prospects.
Summer signing Filipe Luis could make his debut at left back, while Didier Drogba, who has yet to start a game since returning to Stamford Bridge in July, and former no1 goalkeeper Petr Cech are also in contention.
The absence of captain could hardly have come at a more inopportune time for die Knappen, who are already without defensive pair Joel Matip and Felipe Santana. Jens Keller's only real option is, therefore, to pair 19-year-old Kaan Ayhan with either 18-year-old Marvin Friedrich or holding midfielder Roman Neustädter at the heart of his threadbare back four.
Spanish international striker Diego Costa has settled right down to business in west London, scoring seven goals in four league games so far this term. He has plenty of Champions League experience, too, having helped former club Atletico Mdrid reach last season's final.
Schalke could certainly benefit from FIFA World Cup winner know-how in midfield. The 20-year-old only managed 45 minutes in the 4-1 defeat to Borussia Mönchengladbach at the weekend, but - with the ball at his feet - always looks capable of unlocking even the most stingy of European defences.
Jose Mourinho: "[Schalke] will be a better team and a difficult opponent. They can work on their mistakes and improve before the game."
Jens Keller: "It's incredibly difficult for us to deal with so many absences. Chelsea are on another level at the moment."
Chelsea are the only team in English football boasting a 100 percent winning start to 2014/15 after picking up four wins from four in the Premier League. Schalke, in contrast, find themselves not only in the Bundesliga's bottom three, but out of the DFB Cup as well.
Chelsea beat Schalke 3-0 at home and away in the Champions League last season to top the group ahead of the second-placed Royal Blues, who also lost at Stamford Bridge back in 2007, before drawing the return tie in Gelsenkirchen.