United lost the first-leg last night 2-0 in Athens.
"It's a disappointing night," Carrick said. "We came here hoping to win and we haven't done that. We didn't react in the second half until it was too late.
"We had good possession in the first half, controlling the game without really penetrating through their lines and causing them any problems. They didn't really cause us any problems and [Dominguez's] goal came from nothing.
"We didn't start the second half very well: we were a bit sloppy really and they scored the second goal, which put us on the back foot.
"But we're not out of the tie. We are still in with a chance going back to Old Trafford and we'll look forward to the second leg. Don't get me wrong: to score three goals in this competition is tough, but we've done it before and we believe we can do it again."
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