Wales boss Warren Gatland said his side's first-half display was unacceptable as they slipped to a 25-21 Six Nations defeat against England.
The New Zealander said he considered making changes after 25 minutes as England took a 16-0 interval lead.
Wales scored three second-half tries to threaten a comeback, but fell just short.
"I sent a message on at 25 minutes asking if we needed to get some fresh legs out there," he said.
"It was a very poor first half by us. At this level that's just not acceptable from us, so I'm very disappointed.
"Only the players can answer the question why they were so flat or lethargic in the first half.
"There was so much to play for, so much on the line, and unfortunately we didn't turn up in the first 40 minutes."
Wales' title hopes dashed
Defeat ended Wales' chances of winning the tournament.
England were presented with the Triple Crown after the game and will go to Paris next weekend looking for a first Grand Slam since 2003.
Wales can still finish second, but only if they beat Italy and England beat France.
Captain Sam Warburton will go through concussion protocols after being taken off on a stretcher late in the second half.
Gatland said it was too early to know if he would be available to play against Italy, and hinted he might make changes for the match in Cardiff next Saturday.
He praised the impact made by his replacements, singling out hooker Ken Owens for giving his side some "go forward" after coming on.