Chelsea manager Jose Mourinho is prepared to risk Diego Costa's fitness at Manchester United on Sunday, providing the striker can train in full on Saturday.
The £32million signing from Atletico Madrid, who has scored nine goals in seven Premier League games despite a persistent hamstring problem, spent a night in hospital earlier this week with a viral infection.
The 26-year-old could play for the first time since featuring for Spain during the international break at Old Trafford.
"I want to play Diego if he is ready to play," Mourinho said.
"If there's a chance to play, Old Trafford is not a place to protect players. If he's ready to play, he plays.
"He has to show (on Saturday) in training that he's capable of playing. He has to train without any limitations, to make a complete training session with the other guys, without any kind of protection."
Costa missed the Premier League leaders' defeat of Crystal Palace and Champions League win over Maribor.
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," added Mourinho, who revealed Costa has returned to training on his own.
Striker Loic Remy (groin) is out for two to three weeks, but midfielders John Obi Mikel (foot) and Ramires (groin) could 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, while Thibaut Courtois will return in goal in place of Petr Cech, who started against Maribor.
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 was reluctant to discuss his relationship with Van Gaal, who made the Portuguese his assistant at Barcelona.
"Please, he's going to be my opponent, so don't make me speak for half an hour about him," Mourinho added.
"He knows what I feel about him. The world knows, because I never hide. What can I add? I have nothing to add."
United struggled under David Moyes last term and are rebuilding this season, having spent huge sums on players including Angel di Maria, a £59.7million purchase from Real Madrid.
There are similarities with Mourinho's first spell at Chelsea, when he made big-money signings, and the Portuguese, who declined the chance to appraise United so far, expects Van Gaal to get results.
"When you have the funds you have to buy well and you have to coach them well," Mourinho added.
"I know Louis is capable of buying well and coaching well. He will do it. He's good. Let's see how things end at the end of the season. It's too early (to say)."
