Arsenal captain Cesc Fabregas will miss the second leg of his side's Champions League round of 16 tie against FC Porto due to a hamstring injury.
The 22-year-old Spain international midfielder limped out of the weekend 3-1 win over Burnley and has not recovered sufficiently to feature at the Emirates Stadium on Tuesday evening.
Manager Arsene Wenger has previously stated that he might gamble on Fabregas' fitness, telling his club's official website: "I'm ready to take the gamble, but it depends how big the gamble is.
"If it is more than a 50 per cent chance his hamstring goes then I will not take it.
"He felt a tight hamstring (against Burnley) but it had not gone.
"I'm convinced he had put in his mind 'we have to score a goal and then I'll go off' knowing that his hamstring was tight. But we were 1-0 up and I thought we shouldn't take a gamble.
"You look at the numbers of Fabregas this season and it is amazing - 14 goals, 15 assists. He's a fantastic player, with a fantastic attitude and commitment.
"And what people forget is an unbelievable work-rate too. He is everywhere and this season he has made a big step forward, massive."