Arsenal goalkeeper Wojciech Szczesny clatters into Arjen Robben, of Bayern Munich, yesterday.

Arsenal saw goalkeeper Wojciech Szczesny sent off after record-signing Mesut Ozil had missed an early penalty, and eventually went down 2-0 against Bayern Munich in the Champions League last 16 first leg clash at the Emirates Stadium, last night.

There was a blistering start to the European tie – a year on from their last encounter in north London – and the holders could have snatched an early lead when Toni Kroos fired in a 25-yard effort towards the top corner, which Szczesny tipped over.

Yaya Sanogo had been a controversial selection in attack ahead of France striker Olivier Giroud, whose off-field actions have made headlines in recent weeks.

However, the summer free transfer from Auxerre – who has been out for several months with a back problem – saw a close-range shot palmed away by Manuel Neuer, before the German keeper saved a tame spot-kick from Ozil on eight minutes.

There was more drama just before the break as Szczesny was shown a red card for bringing down Arjen Robben in the penalty area – only for full-back David Alaba to side-foot his spot-kick against the base of the post.

Bayern, though, went ahead on 54 minutes with a superb 20-yard strike from Kroos, which was whipped into the top corner past substitute keeper Lukasz Fabianski.

Arsenal tired heading into the final 20 minutes as Robben exploited the space in front of a jaded backline.

Eventually, the pressure told as substitute Thomas Muller headed in a late second goal to all but kill off the tie ahead of the return leg at the Allianz Arena next month – where Arsenal won 2-0 last season, but ultimately lost on away goals.

At the San Siro, Diego Costa headed a late goal to give Atletico Madrid a 1-0 win at Milan after the hosts were twice denied by the woodwork in the first half.

Costa scored at the far post after the Milan defence failed to clear a corner as the Spaniards won a fast, furious and often scrappy and bad-tempered match.

Milan had created the better chances and were frustrated as Kaka had a delightful curling shot tipped on to the crossbar by goalkeeper Thibaut Courtois who also deflected Andrea Poli’s header on to the post in a dramatic first-half spell.

Clarence Seedorf, who won the Champions League four times as a player with three different clubs, made his coaching debut in the competition in charge of Milan.

Milan made a nervous start but nearly went ahead thanks to the brilliance of Kaka in the 15th minute.

Adel Taarabt slipped the ball to Kaka on the edge of the penalty area and the Brazilian produced a delightful first-time shot with his left foot which Courtois just managed to tip on to the crossbar.

Milan were foiled again three minutes later when Taarabt curled a cross over from the right and Poli’s downward header was tipped on to the foot of the post by the Belgian goalkeeper.

Kaka curled another shot just over the top with his right foot, this time from Mario Balotelli’s clever backheel.

Balotelli also had a chance after a dreadful Gabi clearance but he sidefooted his shot wide from the edge of the penalty area.

Kaka had another good opening just before the hour when he collected Abate’s pass, slipped past two defenders and shot just wide of the far post.

Otherwise, the second half was a scrappy affair in which Milan were repeatedly frustrated by Atletico’s tactical fouling in midfield.

They always looked vulnerable and it was no surprise when Costa scored after Ignazio Abate at the near post headed the ball straight up into the air.

Round of 16 (first legs)

Played yesterday
Milan (Italy) vs Atletico Madrid (Spain) - 0-1
Arsenal (England) vs Bayern Munich (Germany) - 0-2

Played Tuesday
Bayer Leverkusen (Germany) vs Paris St Germain (France) - 0-4
Manchester City (England) vs Barcelona (Spain) - 0-2

Tuesday, Feb. 25
Zenit St Petersburg (Russia) vs Borussia Dortmund (Germany) - 18.00
Olympiakos (Greece) vs Manchester United (England) - 20.45

Wednesday, Feb. 26
Galatasaray (Turkey) vs Chelsea (England) - 20.45
Schalke 04 (Germany) vs Real Madrid (Spain) - 20.45

Second legs: March 11/12 and March 18-19.