Wenger said earlier he is willing to take a gamble by playing the unfit Spaniard, but has now conceded there is no chance of a risk.

"We cannot even take a gamble, so he is not available," said the Frenchman.

Fabregas has been in devastating form for Arsenal this season, scoring 14 goals and setting up 15 in the Premier League.

Arsenal trail Porto by a goal, following the Portuguese champions' 2-1 first-leg win.