Chelsea striker Diego Costa was taken to hospital after suffering a rib injury during his side's Capital One Cup loss to Stoke City on Tuesday.
The injury occurred when Costa collided with two Stoke defenders and went down clutching his lower rib area.
After lengthy spell of treatment Costa tried to run off the injury, but he was unable to do so and was replaced by Loic Remy in the 30th minute.
"He's in the hospital," Chelsea manager Jose Mourinho told reporters after the match.
When asked how Costa had sustained the injury, Mourinho replied: "I don't know. I think he punched himself."
Costa's injury is just one of a number of headaches for Mourinho, with his side continuing to struggle to find the form which saw them win the league last season.
Stoke compounded the Blues' woe on Tuesday when forward Jonathan Walters put his side ahead after 52 minutes before Remy netted the equaliser in stoppage time, sending the match to extra time. Neither side could break the deadlock, with penalties required to separate the two teams. It was Stoke keeper Jack Butland who would prove the hero, saving Eden Hazard's penalty to put his side into the quarter-finals.
The midweek defeat continued Chelsea's dismal run, with the Blues having lost five of their opening 10 Premier League fixtures, while winning just one of three Champions League encounters.