AC Milan has confirmed that forward Alexandre Pato has been ruled out for the rest of the season due to muscle problems.

The Brazilian made his return to the team on Tuesday in the club's 3-1 Champions League defeat at Barcelona. However, he lasted only 13 minutes after coming on as a second-half substitute and had to be replaced after suffering yet another muscle injury.

Since January 2010 team doctor Jean Pierre Meersseman says that Pato has suffered 13 muscle-related injuries and that he is still puzzled by the cause.

"His season is over. We'll have to start again when he has healed," Meersseman told Gazzetta dello Sport.

"He's been all over, from Germany to America, in a bid to resolve his fragile muscles. He's been looked at and cured. I've even asked my spiritual therapist to pray for him."

The 22-year-old has been limited to just 11 Serie A games because of injury this season, scoring one goal.