Peter Crouch saw red during the 4-0 Champions League thrashing.
Redknapp admitted: "It was a difficult night. I lost Aaron Lennon just as the team were walking onto the pitch, he didn't feel well enough to play so we had to change that straight away, and obviously to go down to 10 men is difficult, you need a miracle here to win with 10 men.
"Better teams than us would probably have struggled tonight. It was an uphill task, an impossible task. For the first half I thought we did fantastic with 10 men, we had a couple of good opportunities on the break but we ran out of steam, with Gareth (Bale) cramping up, and we lost our right back (Vedran Corluka). It was one of those nights.
"Obviously we're disappointed. What do you do about the third goal? An unbelievable finish, they've got quality players and you need to have 11 to have any chance and be at your best here."