Arsenal FC went top of Group F thanks to substitute Aaron Ramsey's late strike after a cautious contest in which Olympique de Marseille offered long spells of resistance.
A tight, tactical encounter looked destined to finish in stalemate before Ramsey's 92nd-minute intervention. The Welshman had only been on the pitch for 14 minutes when he swept the ball home at the far post after Gervinho had allowed through Johan Djourou's right-sided cross.
Chances had been scarce, although the Gunners did look the more threatening side in the second half, and Steve Mandanda twice needed to save with his feet from Theo Walcott and Robin van Persie. The result takes Arsène Wenger's men top of the section, a point above OM, ahead of the return game in London on 1 November.
Both sides have been strangely off colour in their domestic leagues, which may have contributed to a cagey opening in which Mathieu Valbuena's free-kick – comfortably saved by Wojciech Szczęsny – was the sole effort on goal. Yet as Arteta's influence grew, the visitors began to settle, creating their first chance on 21 minutes when Van Persie's header was cleared off the line by Souleymane Diawara following a left-sided corner.
It had been through solid defending and fine counterattacking that the Mediterranean outfit accounted for Borussia Dortmund last time, and they threatened to repeat the trick with a series of speedy raids before the break. Subdued early on, forward Loïc Rémy burst into life shortly after the half hour, slipping past Per Mertesacker on the byline and cutting in menacingly from the left only to see his shot deflect wide off Carl Jenkinson.
OM's confidence seemed to be returning and Lucho González came close on 35 minutes, flicking Valbuena's cross wide of the far post having ghosted into the box unopposed.
The Gunners tightened up in the second period, Laurent Koscielny in particular showing assurance on his return to France, and the Premier League outfit slowly got on top. Walcott might have opened the scoring on 63 minutes, but after taking advantage of Nicolas N'Koulou's mistake, the Englishman's shot was expertly saved by Mandanda with his boot.
Van Persie was similarly denied by the Marseille custodian as Arsenal entered added time in the ascendancy – and Ramsey had the final say.