Rudiger has been out injured since the start of the season, but is back in Chelsea training now.
The powerful centre-back should return sooner rather than later, but Chelsea will be without him at the weekend when they take on Burnley and tonight when they face Ajax in the Champions League.
Ross Barkley and N’Golo Kante are also both set to miss Chelsea’s game this evening, with the midfielders picking up injuries.
Lampard claims that Barkley should be back in time for Saturday, but there are more doubts over Kante’s fitness.
Lampard said: “Ross will hopefully be fit to train by the time we get back on Thursday, Rudiger has trained with us today which is part of a small programme to have him fit, he's going to be out of contention for the weekend but hopefully soon.
“N'Golo similarly, he's training but we'll see how he is for the weekend. Not clear yet on that one.”
Rudiger’s return should be a boost to Chelsea, although Kurt Zouma and Fikayo Tomori have both performed well at the back in recent weeks in his absence.
Kante, meanwhile, will be a huge miss tonight against Ajax, and Lampard will want the Frenchman back sooner rather than later.
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