Arsene Wenger has admitted that Arsenal were "surprised" by CSKA Moscow's early intensity in Thursday night's Europa League quarter-final second leg at the VEB Arena.
The Gunners led 4-1 from the first leg but found themselves trailing in Russia to goals from Fedor Chalov and Kirill Nababkin.
Danny Welbeck then struck in the 75th minute to give Arsenal breathing space before Aaron Ramsey's stoppage-time goal made certain of progress into the last four with a 6-3 aggregate win.
"I feel that maybe we were a bit surprised by the intensity at the start," Wenger told BT Sport at full time.
"After that we came back. They scored the second, had a chance for the third. It was a good response from us after the break, the first half the distances were too big. At 2-1 we looked good to get to 2-2 and we did.
"We were in trouble in the first half. After moving to a back five we were more stable, didn't concede as many chances. Their second was from distance, but in the box we didn't give anything away."
Arsenal are joined by Atletico Madrid, Marseille and Red Bull Salzburg in the semi-finals of the competition, with the draw taking place on Friday at 12pm.
