After surrendering a two-goal advantage and requiring a late header from Ashley Young to secure a draw, United trail their Swiss opponents by two points with two matches played.
"It's not the end of the world but it's not ideal and we've left ourselves a lot of hard work to do but we are capable of doing that," Carrick told reporters after the match.
"There are no excuses really - we said at half-time that the game wasn't over.
"It was a bit of a shock to find ourselves 3-2 down after being 2-0 up. But we've no excuses, we threw it away. It's not like us at all but I'm sure it's a one-off and that we will bounce back."
United drew their opening Champions League match 1-1 with Benfica.