Chelsea striker Diego Costa could climb out of a hospital bed to play at Manchester United tomorrow.
Jose Mourinho has bemoaned the absence of the £32million signing from Atletico Madrid, who has scored nine goals in seven Premier League games despite a persistent hamstring problem.
The 26-year-old Spain forward (left) missed the matches with Crystal Palace and Maribor and spent a night in hospital earlier this week, but could feature at Old Trafford.
"Diego has a little chance," Mourinho said.
"I'm not saying he can (play). I'm saying that we are trying. We will see what happens between Friday, Saturday and Sunday.
"Everything happened to him. He was obviously injured and he had to go to the hospital with a viral situation that we didn't manage to resolve without being in hospital over one night."
Costa's recovery from his niggling hamstring problem was delayed by the bout of illness, as he was barred from Chelsea's Surrey training base.
"The problem is that being ill obviously didn't help his recovery process because we didn't want him here at Cobham," Mourinho added.
"The medical staff were going to meet him at his house."
Now Mourinho confirmed he had returned to training on his own.
Loic Remy is out of the Manchester United match after sustaining a groin injury in Chelsea's 6-0 Champions League defeat of Maribor on Tuesday night.
Mourinho added: "The only one that I can confirm has no chance is Remy. I would say two weeks, three weeks (out)."
Midfielders John Obi Mikel (foot) and Ramires (groin) could also return alongside Andre Schurrle, who has recovered from illness.
Cesar Azpilicueta is suspended for the first of three matches after his dismissal at Palace, with Filipe Luis likely to replace him.
Thibaut Courtois will return in goal in place of Petr Cech, who started against Maribor.
"I start with Thibaut," Mourinho said.
The Premier League leaders' trip to Old Trafford will be just the second competitive fixture between Mourinho and his one-time mentor Louis van Gaal.
The pair met in the 2010 Champions League final, with Mourinho's Inter Milan beating Van Gaal's Bayern Munich 2-0.
Mourinho, who was the Dutchman's assistant at Barcelona, said: "I don't play against Louis.
"Chelsea plays against Man United. As a young coach to be working four consecutive years - one with Mr (Bobby) Robson, three with Louis - at a club like Barcelona was very important.
"It's not the moment for that. Everybody knows the respect I have for him. I never hide the respect, the relationship and the fact he was an important influence in my career.
"But, please, he's going to be my opponent, so don't make me speak for half an hour good about him.
"He knows what I feel about him. The world knows, because I never hide. What can I add? I have nothing to add."
Mourinho declined to appraise United's season so far under Van Gaal as he attempts to extend Chelsea's unbeaten start to the campaign.
Against David Moyes' United, early in his second spell as Chelsea boss in August 2013, Mourinho opted for a conservative approach at Old Trafford.
He played without a recognised striker, out of choice rather than necessity, with Schurrle as a 'false nine', but this time around will seek victory.
"We go to every match to win," Mourinho added.
"Sometimes matches go in one direction where in a pragmatic way you feel that one point becomes a good result.
"Sunday we go to win. If you give me now one point and I don't go and I don't play, I don't accept the point you give me. I want to fight for the three points."
Mourinho believes United remain a difficult opponent despite the recent travails. He said: "For me it doesn't matter the manager, the moment, the table, the players - Man United is Man United and I always look at them independent of these factors.
"I like to play big matches, I like to play against the best teams. I like to play in the most difficult stadiums.
"I know the risk of not getting a good result is bigger in big matches. But I always like.
"For me to go to Old Trafford - I did it with four different clubs, with Porto, with Inter, with Real Madrid and with Chelsea - I like to go there, I like to play there."
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