Atletico Madrid came away from the San Siro on Wednesday with a 1-0 win over AC Milan in the first leg of their Champions League round of 16 showdown.

The visitors, who currently share the lead in La Liga, dealt Milan the rare home defeat thanks to Diego Costa's header off a rebound in the 83rd minute.

Atleti found themselves forced to play an unaccustomed possession game and still gave up three great chances to Milan late in the first half.

Indeed, the outcome could have been very different but for a spectacular stop by Atletico goalkeeper Thibaut Courtois on a shot by Andrea Poli.

Wednesday's other Champions League tie featured Arsenal hosting Bayern Munich, which prevailed 2-0 over a Gunners squad that had to play more than half the match with 10 men after keeper Wojciech Szczesny was ejected for a rough tackle on Arjen Robben.

Toni Kroos and Thomas Müller scored for Bayern, winner of the 2012-2013 Champions League, while Arsenal's Mesut Özil missed on a penalty in the 9th minute. EFE