According to reports out of England, Chelsea striker Diego Costa has been battling an illness that forced him to spend time in the hospital after returning from international duty with Spain.

Costa had already been struggling with a recurring groin injury, but it has now surfaced that the former Atletico Madrid striker has also been suffering from a ‘stomach illness’ which had him sent to the hospital. Chelsea have not specified what the illness is and/or whether Costa is fully over it, but it is understood that the 26-year-old had symptoms similar to a severe stomach bug.

Should these reports be true, it would explain the level of anger shown by manager Jose Mourinho over the condition of his leading goal-scorer following his return from national team duty with Spain.

“Sometimes you have national coaches and medical departments that want to establish a relationship and they are interested in the players, their physical condition, their habits,” Mourinho told the press last week.

“Others they simply don’t care. This is not something we can resolve. I cannot ring the federations and say I want to speak to the coach, or the doctor wants to speak to their doctor. It’s something I cannot resolve.”

This week, prior to their Champions League match with Maribor, Mourinho informed the media that the only national team coach he has a relationship with is Roy Hodgson of England. The manager fumed that year after year he finds it hard to deal with other national team coaches and he believed that some international sides “don’t care what condition the players come back to their club teams in.”

Mourinho has not included Costa in Chelsea’s last two matches, against Crystal Palace and Maribor, and the manager has stated that he does not expect the striker to be available to face Manchester United on Sunday at Old Trafford.

The Chelsea boss may be forced to start 36-year-old Didier Drogba against United after Loic Remy limped off the pitch after 16 minutes during the club’s 6-0 Champions League group stage victory over Maribor on Tuesday.

Speaking after the match, Remy was hopeful of being available for selection on Sunday.

“We will see with the scan,” the France international said on Wednesday. “I really hope it is not too bad. Fortunately, I stopped playing because I felt something. I don’t think it is too bad, but I felt something. My groin.”