Lionel Messi is expected to miss Barcelona's match against Valencia on Saturday and is a major doubt for next week's Champions League opener at Borussia Dortmund, sources have told ESPN FC.

Messi, 32, has not played for Barca since injuring his calf during his first training session of preseason in August. He missed the club's tour of the United States and hasn't featured in any of their opening three league games.

Barca have never put a time frame on the extent of the problem. It was anticipated he would be back for the draw at Osasuna before the international break, but he didn't feel right the day before the game and wasn't risked.