Arsene Wenger has paid tribute to Arsenal's "exceptional" Danny Welbeck and his ability to deliver when the team are up against it.
England international Welbeck has hit a rich vein of form with five goals in his last five club matches, including a vital goal at CSKA Moscow on Thursday.
The Gunners appeared to be at risk of becoming the latest European giant to let a big lead slip as they saw their aggregate advantage cut to 4-3 in Russia.
But Welbeck stepped up to score and ease the pressure on Arsenal, before Aaron Ramsey netted a second, and Wenger lauded his front man's contribution.
"I would say, above all, the qualities of Danny Welbeck: when your back is against the wall, he looks like he has that extra special motivation in his body and in his head," the manager said.
"That can give you something special. That's something really exceptional and that you do not find in many players."
And Wenger conceded - perhaps like Barcelona, Real Madrid and Lazio - that it was difficult for Arsenal to motivate themselves for the second leg, having won so comfortably in London.
"You could see when you have a big difference after the first game, it is difficult to turn up with the same urgency than if the difference is very small," he said. "That played a part in the first half.
"I felt in the two games [CSKA] played well, especially [on Thursday] they made my heart beat much quicker than I expected it to be.
"We played against a good team. I knew that after the first game and they showed that again tonight - they gave us many problems."
