Tottenham's Jermaine Jenas claims referee Felix Brych showed "inexperience" and was "a little bit rash" in sending off Peter Crouch on Tuesday.
Spurs' hopes of making the last four look all but over after they took a 4-0 beating from Real Madrid at the Bernabeu in the first leg of their quarter-final clash.
"I think the referee was a little bit rash," Jenas said.
"Maybe it was inexperience on his part more than anything.
"At some point you have a word, you just talk to the player, rather than dishing out cards every two minutes."