Ferdinand said: “The Benfica game is very, very important.
“It would be criminal to throw this chance away now, having been in the position we were in.
“I thought we should have won the game in Copenhagen and it was the same against Celtic in Glasgow.
“We would rather be in the position where we had qualified. But now we need to make sure we get a positive result. We have made it difficult for ourselves.”
He added: “We couldn’t have controlled the last two games more than we did without scoring.
“After the Celtic match, it was one of the weirdest feelings ever coming into the changing rooms.
“There were all the emotions. We were angry, upset, almost baffled in a way, as we controlled the whole game.
“We had to finish off a couple of the chances we had and we would have been all right. But we didn’t.
“That is the difference with the Champions League – you have to make sure you kill games off.”