Champions League Group G/FC Porto v Arsenal: No club speaks of the future with quite so much delight as Arsenal. With Thierry Henry out for a month or more, it is natural for Arsene Wenger to dwell on the opportunities this will create for the 17-year-old Theo Walcott over the next few weeks.

That, all the same, must be no more than a digression for a man who can look no further ahead than tonight.

If Arsenal are beaten in Porto while CSKA Moscow win at Hamburg, then Wenger's side will be eliminated from the Champions League. It is more soothing to reflect that they and Porto would both advance to the last 16 if they draw. That would be a convenient outcome for two very concerned parties at the Dragao Stadium but an unspoken agreement should not be taken for granted.

Wenger implies that the teams would settle for a point each only if the game was petering out. "We will go out and try to win the game," the manager said. But he added: "If it's 0-0 10 minutes before the end we will certainly not bombard them with everyone in their box."

It would calm Wenger, all the same, if Arsenal could attack at length, since depending on defence currently holds little appeal. William Gallas has not quite recovered from his calf injury and the side will need him badly at Stamford Bridge on Sunday, when another centre-back, Kolo Toure, is suspended.

Wenger projects imperturbability in the hope that his squad can stay equally composed. "We can never predict completely what will happen," he said. "But we are relaxed, we are united, we have quality and we know how we want to play, so that gives us quite a good chance."

The manager will surely resort to the 4-1-4-1 formation that became such an asset for Arsenal in the run to last year's final. With Tomas Rosicky out for up to three weeks after tearing a groin muscle for the second time this season Wenger does not even have to deliberate unduly about the composition of the midfield.

When it comes to the solo striker role, his Togolese striker, who opened the scoring against Spurs on Saturday, is a natural candidate. "Emmanuel Adebayor is a guy who can fight," said Wenger. "He complements Henry but he can play on his own up front as well."

Arsenal will also be obliged to keep their balance against opponents who are deft counter-attackers and the onus will lie with the Brazilian who deputises as captain while Henry recovers. "Gilberto Silva is a strong leader, much stronger than people expect," Wenger insisted. "When his back is to the wall, he stands up. He is not a penalty taker but the way he took them against Spurs tells you a lot about his character."

Arsenal have experience of performing without Henry but his absence does press responsibility on other figures. "When a player like Thierry is not there it always changes the game," said Wenger. "Naturally the game goes through him a lot. The ball has to go through other players more (in Porto)."

Wenger is thinking about the way the line-up will have to be altered as fixtures pile up. He assumes defenders can play without respite and worries more about keeping the attackers fresh. Even if he does not begin the game tonight, Walcott will soon be more prominent.

"He's a different player today from six months ago," said Wenger. "He is stronger and, when he goes forward one on one in training, he is much more decisive. He's a great finisher. He will play games. It is a good opportunity for him to have more chances than he would have had."

Whatever part Walcott does or not does not play, no one in Arsenal colours should be taken by surprise if the match with Porto proves to be challenging.

As Arsenal flew out Henry spoke about his regrets over his alleged row with Wenger. Henry left training in a huff on Friday after being told he would not be playing against Tottenham the following day or against Porto.

"I have always said, and I will say it again, that I would rather be on the pitch injured than off it," said Henry. "And we had these two very important games coming up. What really upset me is that we beat Spurs but instead of talking about the team, about scoring a goal in open play, there was this speculation about me."

But Henry (29), who was in London's West End for a fashion shoot, insisted he had no regrets about leaving training on Friday. "I would do the same again. But the past 72 hours is finished."

Wenger confirmed Gilberto will lead the side only temporarily and said: "For me Thierry will be captain. At the moment Thierry gets a lot of stick he doesn't deserve, because what he has done for the club is tremendous. He will do a lot of tremendous things for the club again."

CSKA Moscow v Hamburg

CSKA Moscow were handily placed before the last round of fixtures in Group G, when they held a one-point advantage over both Arsenal and Porto. However, a 2-0 home defeat by Porto could prove to be very costly because even a win against Hamburg tonight might see them left to fight a Uefa Cup campaign if the game between Porto and Arsenal ends in a draw.

In that event all three teams would finish with 11 points (and on five points each when results between the three are taken into account) and the goal difference in the matches involved would give Arsenal top spot with Porto second. The Russians must look to triumph in Germany and then pray there is a winner at the Estádio do Dragão.

All that remains for Hamburg is to try to gain their first points. They were assured of finishing in last place following their 3-1 loss to Arsenal in London in the last series.