Robin van Persie and Nemanja Vidic are both ruled out of Manchester United's Champions League game against Bayer Leverkusen.
"They are both injured," United boss David Moyes said of striker Van Persie and defender Vidic.
"Nemanja Vidic had concussion and Robin has a problem with his groin.
"Neither of them are long-term but they are not quite ready yet."
The injured duo missed the 2-2 draw at Cardiff on Sunday and neither boarded the plane to Germany on Tuesday. Vidic had trained previously before the squad departed.
Midfielder Marouane Fellaini, meanwhile, automatically misses Wednesday's match through suspension.
Leverkusen also have their injuries, with Germany winger Sidney Sam ruled out after he tore a thigh muscle after just four minutes of their 1-0 win at Hertha Berlin on Saturday.
A win for either team will secure their path into the last 16, although if they were to draw they would need Ukrainians Shakhtar Donetsk lose to Spanish side Real Sociedad in the other game of Group A.
Despite conceding a disappointing injury-time goal against Cardiff in the Premier League on Sunday, Moyes' United side fly to Germany with confidence, with the Red Devils on a 10-game unbeaten run.
Sami Hyypia's Leverkusen are second in the German Bundesliga, just four points behind leaders Bayern Munich, and also go into the game with confidence after recording eight consecutive home victories in the Champions League group stages.
The German giants lost 4-2 to Manchester United in the group's opening round, yet Leverkusen have now picked up seven points in the following three games.
"We have always played well at home," boasted the former Liverpool legend Hyypia.
"It won't be easy for Manchester United and, of course, we really want to win."
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