The Londoners were weakened coming into the second round fixture following injuries to Robin van Persie, Andrei Arshavin, Eduardo, Alex Song, William Gallas and goalkeeper Manuel Almunia.
But despite the deputising Lukasz Fabianski being found culpable for both goals in the 2-1 defeat, his manager Arsene Wenger refused to criticise his performance.
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The young Pole palmed a wicked Silvestre Varela cross into his own net after just 11 minutes, before picking up a Sol Campbell back-pass that led to the second.
Ruben Micael wasted no time in squaring the ball to the quick-witted Falcao for the simplest of finishes past the still arguing goalkeeper.
Fabregas could not argue with the ingenuity of the quick free-kick that gave the Portuguese side a slender lead going into the second leg.
When asked whether the goal should have stood, the Gunners' skipper answered: “I don’t know. I have no idea to be honest. Maybe as a player I would have done the same.”
He described the costly errors as “schoolboy’s goals,” adding: “What can you do? Nothing, nothing to complain [about].”
However, the Spaniard was left especially frustrated as he felt the Gunners had been performing well up to that point.
“After the second goal we went down, maybe we are still a little bit soft in that aspect as a team. When we concede a goal maybe sometimes we are not strong enough to lift ourselves up.
“That’s what happened really, we were not strong enough to stand up and play well but until the second goal I think we were having a very good game.”
