Arsenal defender William Gallas has broken down in training this week.

The Mirror says Gallas, 32, broke down in training on Tuesday after a recurrence of an injury and is out of tomorrow's trip to Stoke.

But Arsenal boss Arsene Wenger admits that he does not know when the French centre half will return which also puts a major question mark for the Champions League second leg with Porto in a fortnight.

Wenger said: "With Gallas we don't know. Gallas has had a recurrence of his calf injury. He tried hard on Monday and Tuesday but on Tuesday he had a little problem again. We will have to assess that."