Diego Costa’s mystery illness forced him into hospital on return to Chelsea from Spain duty

The mystery over Diego Costa’s condition has deepened after it emerged that the Chelsea striker was forced to spend time in hospital after returning from international duty with Spain.

Costa is struggling with a groin injury, but has also been battling an illness that forced him to go to hospital. Chelsea have not specified the illness and whether Costa is fully over it, but it is understood that the 26-year-old had symptoms similar to a severe stomach bug. That he has two problems goes some way to explaining the level of anger felt by Jose Mourinho, the Chelsea manager, over the condition in which his leading goal-scorer returned to the club last week.

Costa has missed Chelsea’s past two games, against Crystal Palace and Maribor, and Mourinho claims that he does not expect him to be fit to face Manchester United on Sunday. It is understood that Costa did not train yesterday.

The players that faced Maribor on Tuesday were given the day off, but Costa would have been expected to train if fit in a bid to be ready to play some part against United.

Mourinho reluctantly stated that Costa had aggravated his hamstring problem, but it is believed that it is actually the striker’s groin causing him discomfort.

Chelsea should find out today whether Loïc Rémy stands any chance of making the trip to Old Trafford after he injured his groin against Maribor. Mourinho claimed Remy would be unlikely to face United, but the Frenchman offered a different view.

“We will see with the scan,” Rémy said. “I really hope it is not too bad. Fortunately, I stopped playing because I felt something. My groin. It was before I scored, it was a bit stiff – even my run did not feel very comfortable. if I’m not feeling very good it’s better to leave for another player who is 100 per cent.

“Yes it’s frustrating, because I had a chance to play because Costa is injured, but I am not afraid. I don’t think it is really bad. We will check and I really hope to play again this weekend.”

If Costa and Rémy are ruled out of the United clash, then the 36-year-old Didier Drogba will be Mourinho’s only fit senior striker.

Drogba is still attempting to fully recover from the ankle injury that has troubled him since his return to Chelsea. After scoring his first Chelsea goal on Tuesday since his Champions League-winning penalty in 2012, Drogba said: “It was a nice to score. OK, I would have preferred to have play under different circumstances because we have an injured player and I hope he’s going to be fit for the weekend. But it was good to play 75 minutes.

“I need time because before signing here I didn’t play for two or three months then I had this injury that kept me out for a while, so I need more games. But I’m training hard to be back to full fitness. It’s up to the manager to decide who’s going to start against Manchester United, but if you were a player how would feel if they say you can play at Old Trafford? You’ll be happy.”

Mourinho fielded André Schürrle as a makeshift striker at Old Trafford last season and the German in expected to have recovered from illness and be fit to face United if required.