Neither problem is directly related to the knee problems that forced him to retire from the game briefly. Reds boss Sean O'Driscoll said: "He has a patellar tendon problem in his left knee, which is probably as a result of the previous problems he has had in his right knee. "Patellar tendon problems can be awkward injuries. Owen Hargreaves is probably the most well-known case of it. "You can give people injections to get through, but if it becomes a chronic issue, it can be career threatening. "We are making sure we do not risk that, because he is not our player. He has been down with Chelsea for a few days since the Palace game. "On top of that, he did get a couple of knocks on his right knee on Tuesday, which is going to get scanned just to check. "He is a valuable player to Chelsea. But we will see how he is today (in training)."