Barcelona forward Lionel Messi [Images] is a serious doubt for next week's Champions League semi-final, first leg against AC Milan after being ruled out of Friday's Primera Liga match against Villarreal.

The teenage Argentine international has been out of action since the beginning of March when he tore a thigh muscle during the second leg of his side's 3-2 aggregate victory over Chelsea, but was expected to have made a recovery ready for the Milan match.

Barcelona medical staff said that the 18-year-old had experienced problems with the injured leg while training on Tuesday.

"Messi felt pain and serious muscle fatigue in the injured area during the final stages of his treatment," the club said on its website on Wednesday.

"Treatment will continue until the player can rejoin the group without any recurrence of the symptoms."

Messi has been one of Barca's most exciting and dynamic players this season but the latest injury set-back means that Sweden striker Henrik Larsson [Images] is likely to retain his place in the starting lineup for the Milan match.

Mexican defender Rafael Marquez and midfielder Thiago Motta are also doubtful for Tuesday's game at the San Siro. Both players are suffering from thigh muscle injuries.