1 Arsenal are still capable of the mundane

"Five Alive" screamed the headline on the matchday programme, and it was not a reference to the mixed fruit drink. Arsenal's 5-3 triumph at Chelsea had been hailed for its restorative powers but this was a reality check to deflate the mood. As if to prove a handful of days can be a long time in football, Robin van Persie, the hat-trick hero of Stamford Bridge, who was a substitute here, messed up his team's best chance with an undercooked chip. There was the distinct lack of any stardust. It was all rather laboured. Still, Arsenal are top of Group F, they have a better head-to-head record with Marseille and third-placed Borussia Dortmund have yet to come to the Emirates. One fan summed things up as he departed. "You cannot win 5-3 every week."

2 Gunners' defending is still under the microscope

It was a curious night for the Arsenal defence, who had been asked by Arsène Wenger to show improvements but continued to look somewhat flaky. André Santos cannot have dreamed of stoic defending when he grew up in Brazil, and it shows. The left-back looks more comfortable when marauding forward but at the back he lost his bearings. He struggled to get to grips with Loïc Rémy. The maverick edge in Arsenal's rearguard was illustrated by Wojciech Szczesny, who performed a Cruyff-turn to beat an opponent on the edge of his penalty area. Heart-stopping stuff. Individual errors and a certain slackness pockmarked all of the defenders' games and yet Marseille did not score. Wenger will cherish the ends rather than the means.

3 Park Chu-young fluffed his lines

It was a big night for the South Korea striker, his appearance from the start representing his first non-Carling Cup action for Arsenal since his £3m transfer from Monaco. He had large boots to fill – Van Persie's annus mirabilis has been well-documented. The Dutchman had 33 goals in 37 appearances for him going into this one. Nobody expected Park to put Van Persie in the shade but he gave the crowd nothing to get excited about. He showed flashes of aerial ability and plenty of honest running but was a peripheral figure, easily contained by the Marseille centre-halves. When the player who likes to be known as Ju had his only glimmer of a chance, in the 30th minute and from Theo Walcott's pass, his first touch was heavy. Wenger had no option but to replace him with Van Persie.

4 L'OM earned plaudits

This was a different Marseille to the one Arsenal encountered two weeks ago, in both tactical and philosophical terms. Didier Deschamps, as he has done in Ligue 1 of late, where results have picked up, played his version of a 4-4-2, with Mathieu Valbuena pushed up with Jordan Ayew; Rémy on the right and André Ayew on the left. Bruno Cheyrou also pressed from his central midfield role. There was quicksilver attacking thrust about the visitors; at home, they had rather disappeared into their shells. Rémy had the beating of Santos and although he was theatrical on more than one occasion Valbuena looked classy. With the technique and pace of the Ayew brothers also a feature, the visitors ensured it was a nervy night for Arsenal.

5 Wenger's selection demonstrated his intent

The manager bears the scars of last season's competition, when his tinkering in the second half of the group phase saw Arsenal slip, finish second and then draw Barcelona in the last 16, with predictably disastrous consequences. The omissions of Van Persie and Laurent Koscielny apart, Wenger's starting XI were arguably as strong as possible and it advertised his desire to see off the challenge of Marseille and step boldly towards the knockout phase as group winner. Koscielny's omission was intriguing. He has suffered from aberrations and heavy criticism but he has been in excellent form of late. Wenger even singled him out for praise in his programme notes. It was tough on Koscielny and it raised a question as to whether Wenger might prefer to partner Thomas Vermaelen with a taller player, like Per Mertesacker. Or, simply, whether Mertesacker was in need of a confidence boost after his toils against Chelsea.