Arsenal blinded by delight

Arsenal trotted happily into the knockout phase by topping their group because of PSV Eindhoven's failure at Panathinaikos. They also ended on a note of glee when the substitute Robin van Persie dinked in a fifth goal. They thereby equalled the club's record win in the competition, even if it was far harder to run up this score against Internazionale in Milan last year.

Footballers are under a professional obligation to scrutinise good news. This may have been a second victory in four days to soothe Highbury, but Arsenal's satisfaction should be tempered. Rosenborg were too poor to constitute a benchmark and they have now been beaten in 15 of their last 16 away fixtures in this tournament.

The specific doubts that Arsène Wenger's team have about themselves were not quashed here. Cesc Fábregas, at 17, continued his record-breaking by becoming Arsenal's youngest scorer in European competition, but it was less apparent that he and the 20-year-old Mathieu Flamini can form the partnership to clamp down on Chelsea this weekend.

Neither man is to be faulted for that, but Arsenal fans may wonder how they are to counter Frank Lampard and Claude Makélélé on Sunday when they did not have the knowhow to check Rosenborg, who swept forward with some ease despite their limitations. The continued suspension of Patrick Vieira, combined with the injuries to Edu and Gilberto Silva, presents a grave problem to Arsenal.

Rosenborg's advances also highlighted the tangled issue that Wenger has to unpick before he next names a team. Manuel Almunia sprang to make an outstanding save from Harald Brattbakk's volley in the 17th minute that could have brought the Norwegian champions level at 1-1. That highlighted the shot-stopping talent that has swayed the Arsenal manager into selecting him ahead of Jens Lehmann. Later, however, Almunia was nervous and clumsy, dropping a cross to let Erik Hoftun cut the deficit to 3-1 with a deflected shot in the 38th minute. That incident had little significance, though, and the damage to Almunia's reputation is not necessarily fatal.

Wenger argues plausibly that Chelsea will be given a severe test, but this was only nominal preparation. Though Arsenal would have been eliminated had they lost, Rosenborg were therapists rather than tormentors. The atmosphere was so soothing that it might have dispelled the migraine that ruled out Freddie Ljungberg. The Swede is now a doubt for the clash with Chelsea.

The Highbury crowd, in any case, doted once more on Arsenal's attacking prowess. José Antonio Reyes, muted since his pounding by Manchester United boots at Old Trafford in October, proved that his confidence is healing nicely. Dennis Bergkamp, whose comeback from injury restored wit to the build-up, set the winger running on the left in the third minute and he skipped inside the hapless Torjus Hansen before finding the net at the near post.

When Flamini's hard tackle scooped the ball forward in the 24th minute, Thierry Henry, sprinting behind Hansen, lobbed the ball home. Arsenal had a festive merriment about them six minutes later when Bergkamp played in a cross and Robert Pires laid it off to Fábregas. The teenager teased it away from Hoftun with his right foot and then glided the ball past Espen Johnsen for another goal.

Rosenborg were soon to see Hoftun head a corner on to the post, but Arsenal's lapses were more disturbing as a portent for games to come than an immediate worry here. As if to show they were not distracted when the Rosenborg captain did score, Wenger's side soon re-established a three-goal margin. Henry, when clear, got himself into a tangle but he went down over Johnsen's leg and Pires drilled the penalty home in an understandably relaxed manner.

In their own limited fashion, Rosenborg showed a commendable endeavour to maintain an attacking approach whenever possible. The shielding of the Highbury back four was only an academic issue last night but it could be the key to the outcome against Jose Mourinho's efficient team.

On another night the fans might have departed crowing over success for Arsenal while Chelsea had been losing to Porto. No one, though, could fool themselves that either outcome is a trusty guide to the relative standings of the clubs. That dispute can only be settled when they come face to face.