Arsenal have been left with a mountain to climb to progress in the Champions League following a 4-0 first-leg defeat to AC Milan at the San Siro.
The Gunners were second best throughout and fell behind in the 15th minute courtesy of a spectacular volley from former Tottenham man Kevin Prince-Boateng.
Milan doubled their advantage before the break thanks to a close-range header from ex-Manchester City forward Robinho.
The Brazil international added his second of the game after half-time, angling a right-footed drive beyond Arsenal keeper Wojciech Szczesny.
Milan added a fourth in the 79th minute when Zlatan Ibrahimovic converted from the penalty spot after he was brought down by Johan Djourou.
Szczesny admitted Arsenal were outclassed.
He told ITV: "We didn't have the best of games but you have to give credit to Milan. They punished us on every occasion and scored some quality goals.
"They deserved to win. It's very disappointing day for us and hopefully we can pick ourselves up and challenge them in the second leg."