"Will I risk Fabregas? It depends how big the gamble is," Wenger told the Guardian.
"I'm ready to take the gamble but, if it is more than 50% chance that his hamstring goes, I will not take it. He has a little chance of playing. Sol Campbell will be available [after a groin injury]; William Gallas, no.
"Cesc felt a tight hamstring but it had not gone," said Wenger, after Fabregas played his part in Arsenal's home win against Burnley on Saturday.
"I'm convinced he had put in his mind 'we have to score a goal and then I go off', knowing that his hamstring was tight. We were 1-0 up and I thought we shouldn't take a gamble."
Arsenal entertain Porto on Tuesday night seeking to overturn a 2-1 first-leg deficit and book a place in the quarter-finals.
- Football.co.uk staff