Manager Arsene Wenger hailed Theo Walcott after his 15-minute cameo helped to rescue Arsenal from Champions League misery against Hamburg.

The 17-year-old substitute inspired a late improvement in Arsenal's performance which produced two goals in the last seven minutes to secure a 3-1 victory.

His pass put in full-back Emmanuel Eboue to defeat Hamburg goalkeeper Stefan Wachter at his near post just as Arsenal were running out of fresh ideas.

Then the former Southampton player launched a right-wing cross which his fellow substitute, on-loan Brazilian Julio Baptista, headed home for his first Arsenal goal.

Wenger said: "We will give Theo more games now - because there are so many of them coming up. When he came on he provided power and pace - especially when he switched from the left to the right. And it helped us master Hamburg physically."

Walcott's contribution was timely, as captain Thierry Henry will miss Arsenal's crunch final match in Group G.

Henry must sit out the match against 2004 winners Porto in two weeks' time after collecting his third booking of the tournament against Hamburg.

Henry missed out on a goal against Hamburg, Robin van Persie cancelling out Holland team-mate Rafael van der Vaart's stunning early strike which had silenced the Emirates Stadium.

Wenger said: "In these Champions League games which are played with such intensity, the last 10 or 15 minutes can often be decisive. And we made a convincing comeback."

Wenger has handed only one Premiership start to Walcott, in a 3-0 win against Watford.

The England Under-21 star may be required to play a greater role against Porto, given Henry's ban.

"It is a blow, of course, losing Henry for the game in Portugal," said Wenger, "but we will go there and do it without him."

Arsenal were Champions League finalists last season and will need just a point against Porto, who beat CSKA Moscow 2-0 last night, to go through to the last 16.

Porto would also qualify if the game ends in stalemate, ending CSKA's hopes of progressing.

Wenger said: "I'm sure both Porto and ourselves will fight for a win but if it finishes in a draw neither team need be disappointed."

Arsenal will hope to improve from a defensive perspective after failing to clear their lines before Van der Vaart fired Hamburg ahead last night.

But Wenger said: "This should convince our players they can come back from behind and win.

"They just refused to accept defeat and never felt sorry for themselves after hitting the bar and post after losing a goal."