It cancelled out Alexandre Lacazette's superb headed goal which came on the hour after the Gunners piled the pressure on a struggling Atletico who had Croatian defender Sime Vrsaljko sent off after getting two yellow cards for tackles in the first 10 minutes of the game.

Arsene Wenger named David Ospina in goal for the game rather than usual first choice Petr Cech for what will be his final European match in charge of the Gunners at the Emirates Stadium.

The rest of the Arsenal side was as expected, Jack Wilshere and Mesut Ozil recalled after missing the weekend win over West Ham with minor complaints.

For the visitors, Diego Costa was only fit enough to be included on the bench after recovering from a hamstring problem.

Arsenal started brightly, Lacazette having a couple of early chances, and they received a boost when Atletico were reduced to 10 men after only 10 minutes.

Vrsaljko, booked for an early challenge on Jack Wilshere, picked up a second yellow for a late tackle on Lacazette and was sent off.

Atletico boss Diego Simeone was incredulous on the touchline and was dismissed by French referee Clement Turpin shortly afterwards for another over-the-top reaction to a Hector Bellerin foul.

Arsenal's impressive start continued but a number of half-chances were passed by before Welbeck drew another good save out of Oblak, with Laurent Koscielny thrashing wildly wide at the back-post following the resulting corner.

Arsenal's impressive start continued but a number of half-chances were passed by before Welbeck drew another good save out of Oblak, with Laurent Koscielny thrashing wildly wide at the back-post following the resulting corner.

The busy Lacazette, who was close to joining Madrid last summer before their transfer ban paved the way for Arsenal to step in, wanted a penalty but went down too easily under pressure from Diego Godin.

Nacho Monreal, who opened the scoring in Sunday's win over West Ham, flashed a half-volley wide with the opening 30 minutes played almost entirely in the Madrid half.

Griezmann looked to change that, finally forcing David Ospina into meaningful action with two driven strikes kept out well by the Colombian.

The hosts seemed to be running out of ideas as the second half began in a similar way to the first, but the deadlock was finally broken just after the hour as Lacazette rose high to head home Wilshere's looping cross.

Atletico lost possession on the edge of their own area, Wilshere was played in down the left and the midfielder stood up a cross for the French striker to head home.

Wenger's path as Arsenal boss has not been smooth in over a decade and his side managed to all-but gift the visitors what could prove a pivotal equaliser.

A long ball forward was not dealt with by Koscielny, whose clearance hit Griezmann with the striker's first shot squeezing through Ospina's legs before he converted past the back-tracking

Shkodran Mustafi, who had already slipped over.

Oblak denied Aaron Ramsey with a fine late save to set up what promises to be an enthralling second-leg in Madrid.

This was Wenger's final home European tie in charge after he announced last week he will step down in the summer after over 21 years in charge but it ended in now familiar disappointment.