Arsene Wenger has maintained that Arsenal cannot use the absence of injured captain Cesc Fabregas as an excuse for failure in tomorrow night's crunch UEFA Champions League clash against Porto at the Emirates Stadium.

The influential Spanish international suffered a recurrence of a hamstring problem during the Gunners' 3-1 victory over Burnley in Saturday's league match and limped off after firing Arsenal ahead in the 33rd minute.

Wenger has admitted that the loss of Arsenal's talisman, who has an outside chance of returning for the trip to Hull on Saturday, is a big blow. However, the Gunners boss insists his side have the quality to secure their place, with or without Fabregas, in the quarter-finals. Arsenal lost the first leg, held in Porto, 2-1 but a 1-0 win at home would be enough to send them past the Portugeuse.

Ideally we wanted him to be there, but we want to qualify and the absence of Cesc is no excuse at all.
Arsenal manager Arsene Wenger

"Cesc has a hamstring problem and we could not even take a gamble with him," said Wenger. "I was hoping he would recover after the Burnley game because we were cautious with him."

"We don't know how long he will be out. He is having a scan today and we are convinced it will only be a short time. He has a small chance of getting back for next weekend against Hull, but to play him again [tomorrow] would mean significant damage.

"Ideally we wanted him to be there, but we want to qualify and the absence of Cesc is no excuse at all. We have enough players and a strong enough squad to get round that and have enough chances to qualify."

Fabregas spent several weeks on the sidelines earlier this season because of a similar problem, yet remains Arsenal's leading scorer this season with 17 goals. Wenger feels this latest fitness set-back is not about player burnout. "I cannot fault Spain, they only played him in one half [against France]," said Wenger, "Cesc has given a lot recently. It is a re-occurrence in the same hamstring so we have to find out why it creates some problems."

With Fabregas out, France international Samir Nasri could move into the centre of midfield, alongside Cameroon defensive midfielder Alex Song, whose domestic two-match ban does not apply in Europe. Wenger feels the 22-year-old, who suffered a fractured leg in pre-season, has come a long way since arriving from Marseille during the summer of 2008.

"In the last few weeks he has got stronger and more confident," said the Arsenal boss.

"He is very versatile, can play defensive midfield, attacking midfield and on the flanks. We have a few players like that and I love that.

"Samir has adapted very quickly. He is a very intelligent boy, a quiet boy, he analyses what is happening on the pitch very quickly and has good technical potential."

Arsenal have not overturned a first-leg deficit in European competition since the UEFA Cup tie against Hajduk Split during the 1977/78 season. In the UEFA Champions League, the Gunners went out after an away defeat to Bayern Munich in 2004/05, lost to PSV Eindhoven in 2006/07 and were ejected from the competition last season by Manchester United after being outplayed over both legs.

Wenger however, maintains that tomorrow will be different. "This time, we have scored," said the Arsenal boss, "When you lose 1-0 away from home it is a difficult game because when you start the next game you know it is almost over because you have to score two or three goals to qualify. This time it is different; if we score one and do not concede then we will qualify."

Porto were overwhelmed 4-0 on their last visit to Emirates Stadium in September 2008. The results remains the Dragon's worst away reverse in the competition.

Wenger feels that result will count for nothing when the Portuguese side return to north London tomorrow. "I do not think anyone will be complacent," he said, "We know it will be a tricky game, but we believe we can do it. We have good confidence, we are in a good position, so let's go for it."