West Brom boss Roy Hodgson sympathised with defender Craig Dawson after his error set up Norwich's winner in their 2-1 victory on Saturday in the FA Cup.
Canaries substitute Simeon Jackson netted the winner five minutes from time by capitalising on Dawson's mistake.
Baggies striker Marc-Antoine Fortune had earlier cancelled out Grant Holt's ninth goal of the campaign.
Hodgson said: "It is one of those no-brainer mistakes and I feel sorry for him - and he hadn't had a bad game up until then. Those errors do occur.
"I am sad to lose because the performance was one where we didn't deserve to lose the game, although we didn't really want to go to Norwich midweek for a replay.
"But now we can concentrate on our main priority, which is staying in the Premier League."