The damage to Cesc Fabregas's hamstring is only minor, Arsène Wenger was at pains to point out yesterday. But the damage to Arsenal hopes of progressing further in the Champions League could be far more serious. Fabregas was yesterday described as "the spirit of the team" by Arsenal's goalkeeper Manuel Almunia, an observation which understates the influence the 22-year-old exerts.
The injury to Fabregas, a recurrence of the hamstring tear that kept him out for a month over the Christmas period, comes at a time when Arsenal already have to cope without two other key figures. William Gallas pulled his calf muscle again in training on Sunday, aggravating the injury that had kept him out of the last four games, and will be sidelined for an indefinite period while Robin van Persie is still recovering from the ankle he broke while on international duty with the Netherlands in November.
Wenger recognised the situation when he said: "It will be amazing if we get through. It is true that at the start of the season you would want Fabregas, Van Persie and Gallas to be the spine of the team. Without them we can show that we are still strong enough to do it."
In their places tonight at The Emirates, with Arsenal needing to overcome the 2-1 defeat they suffered in Estadio do Dragao three weeks ago, are three players who are all indebted to the faith shown in them by the Arsenal manager.
In the absence of Fabregas, the task of playmaker is likely to fall to Frenchman Samir Nasri. The former Marseilles midfielder is only a month younger than Fabregas, yet in footballing terms he is very much the Spaniard's junior in every respect. Signed for £12.5m in 2008, Nasri has yet to live up to the hype that surrounded his move. His progress has been hampered by a broken leg suffered in training during the club's pre-season tour to Austria last July, but since his return in December he has shown glimpses of his potential.
Nasri has most regularly appeared on the flanks, but his close control and ability to both see and deliver killer passes could make him better suited to life in the middle of the pitch. Wenger said: "He started with a fibula fracture at the start of the season and after two months it took him a while to get back to his best. But in the last few weeks he has got stronger and more confidence. He is very versatile. He can play defensive midfield, attacking midfield and on the flanks. We have a few players like that and I love that. He has adapted very quickly. He is a very intelligent boy, a quiet boy. He analyses what is happening on the pitch very quickly. He has good technical potential."
In many respects, Wenger could have been talking about half a dozen of his team. So many players in red show "good technical potential" but against Porto the Gunners need determined characters to see them home as Arsenal have never overcome a first-leg away defeat in the Champions League. Their European record shows only one such comeback, in the Uefa Cup in 1978-79 when they lost 2-1 away to Hajduk Split but recovered with a 1-0 victory at Highbury.
It is on nights such as these that Wenger can thank his lucky stars for Sol Campbell. The 35-year-old signed a short-term contract in January, and has become a key figure with Gallas out for two to three weeks at least. Campbell played and scored in the first leg in Porto, and his experience tonight could be vital. It was not a situation that Wenger envisaged when he re-signed the former England man.
Wenger said: "It was unexpected that Sol would play so many games, but it is also good because I think it was the right decision to bring him back. Sol is a guy who gives everything when he is on the pitch.
"Sol wants to win and he can spread that through the team and give advice. We want to win this game but we also need to be patient maybe and it is important to keep your head. He gives us a good mixture, it is not only him, but there is a good blend of youth and experience. Without Fabregas we will have to share the responsibility."
Nicklas Bendtner is the third player with plenty to prove tonight. He missed three sitters against Burnley at the weekend, triggering a spate of jokes about his fallibility in front of goal. Wenger believes the man dubbed the "Pantomime Dane" has enough self-belief to see him through.
"He is one who can take remarks and criticism and analyse it without being offended," the Arsenal manager said. "He can face his problems and analyse it and change his behaviour. I don't know what he said to the players but he has not fooled himself. He knows that he could have scored."
Robbed of Fabregas, Gallas and Van Persie, Wenger has to pin his hopes on Nasri, Campbell and Bendtner, a trio of players who owe the Arsenal manager a debt of thanks for his unfailing support. Tonight would not be a bad time to start repaying him.
Tough tasks facing the stand-ins
Campbell v Hulk
Campbell will have to be aware of counter-attacks led by Hulk. The Brazilian is desperate to take a rare chance to shine. He is suspended from domestic football after a tunnel scuffle with stewards.
Nasri v Raul Meireles
Nasri is tasked with providing passes like the one for Arsenal's first goal against Burnley on Saturday. But he can expect some rough stuff, as Meireles was guilty of kicking Cesc Fabregas in the first leg.
*Bendtner v Bruno Alves
Arsenal's Danish striker suffered a bout of nerves against Burnley, but is likely to retain his place. Porto's experienced stopper Bruno Alves is likely to be a busy man with the Gunners needing to score to progress.