Atletico Madrid has lost club captain Koke to a muscle injury at almost the worst possible moment of the season.

The club informed on its website that Koke "ended the game last Saturday against RC Celta experiencing some discomforts," and adding that "the midfielder underwent some tests following the match, and the medical tests conducted by the medical staff confirmed that the captain has suffered an injury to right leg."

Atletico explained that he will "undergo physiotherapy session and recovery work in the gym," although the club doesn't say when he will recover, the Spanish sporting press indicated the injury is "not unimportant," meaning Koke could be out of action for several weeks.

The injury came a week before Atletico's visit to FC Barcelona in the first leg of its Copa del Rey semi-final tie and a fortnight ahead of the first leg of the knockout stage of the Champions League, where they could possibly face Bayern Munich or local rival, Real Madrid.

Atletico also has some vital games in La Liga coming up as it looks to make up its one-point deficit with FC Barcelona and Real Madrid, with a visit to an improving Valencia next Saturday and a home game against fourth place Athletic Club Bilbao in the following weekend.

Atletico coach Diego Simeone has already lost Pablo Barrios for the visit to Valencia after the midfielder's red card in Saturday's 1-1 draw at home to Celta.