The Gunners headed to Porto without five first-team regulars, including goalkeeper Manuel Almunia and Russian playmaker Andrey Arshavin.

With centre-half William Gallas, defensive midfielder Alex Song and Croatia striker Eduardo also not among the 18-man travelling party, the Gunners are somewhat light as they prepare for the first leg of their last-16 clash.

Wenger, though, insists being low on numbers should not be an issue for the Barclays Premier League side, who did not have a game at the weekend.

"It is difficult to say how long they will be out," said the Arsenal manager. "But it is not a serious concern.

"The concern is that the players who are here perform at their best tomorrow.

"It is part of the season that you do not always have all the players available to select the team but I am not bothered by that."

With Gallas unavailable because of a calf problem, veteran former skipper Sol Campbell could be in line for his first European appearance with the Gunners since leading them in the 2006 Champions League final against Barcelona.

The 35-year-old has been used only twice since securing a shock return to the club he captained to so much success alongside the likes of Thierry Henry and Patrick Vieira.

Wenger believes former England international Campbell still has plenty left to offer.

"Sol's experience can be important tomorrow," said the Arsenal manager.

"For a central defender, it is a bit special [to still be playing at 35] but, as long as you are hungry to work hard to keep yourself fit and you are not bothered by injuries, then a central defender can play three or four years longer than a striker."

Arsenal have seen their domestic title hopes reborn after the top two both dropped points in the last set of Premier League matches.

Wenger, though, knows full well the young Gunners will tomorrow face a stern test of their European credentials against the Portuguese champions, beaten 1-0 here by Chelsea in the group stages and by Cristiano Ronaldo's wonder strike for Manchester United in last season's quarter-final.

"It is always difficult in Porto - they always have a team who is committed and technically very good," said Wenger, whose side have yet to win in Porto, following a 2-0 defeat when already safely qualified in December 2008 and a goalless draw four seasons ago.

"You respect a team like Porto because you know they will always give you a good game."

The Arsenal manager added: "It is the last 16, a cup draw, so it is always tight.

"We have 180 minutes where we have to be on top and no-one can predict what will happen.

"We will try to do our best."

With Arshavin and Eduardo both unavailable, Wenger could turn to Nicklas Bendtner to lead the attack.

The 22-year-old Denmark striker has just returned to fitness following a three-month lay-off after groin surgery, which was part of the reason the Arsenal manager did not venture into the January transfer market for another forward.

Wenger said: "I think we will see the best of him now as he is getting to the best age for a striker.

"Of course, he will still improve and learn a lot but, at 22, you have to start to play at the top level."

The Arsenal manager continued: "Nicklas is a boy who has a big potential.

"He arrived at the age of 15 and we work very hard with these players to get them to a level where they are today.

"Of course, we do not believe in a player for four or five years and then suddenly stop because people say you should buy a striker.

"We have a line of conduct and we keep believing in what we have done up until now and we hope they pay us back."

Bendtner believes the current crop of Arsenal youngsters can deliver.

He said: "We have a great group.

"All the players here have proved they belong at the top level and they have done fantastically well."