The West Brom manager says that his side will have to dust themselves down and try to focus on the visit of Manchester United next Sunday.
Clarke said: "It is the poorest we have played all season. We were looking to break the 50-point mark but today Norwich were hungrier and sharper than us, it was their day.
"It's been a more difficult second half of the season but today certainly wasn't our day."
The game changed on Norwich's second goal gifted to the home side by a rare mistake from Ben Foster, but Clarke refused to blame his keeper.
Clarke added: "Ben's mistake was decisive but he's been great all season.
"We want to finish in the top eight if we can and we'll try and focus on Manchester United next week which will be another tough game."