James Haskell conceded England had not been good enough during the Six Nations after a 24-15 defeat to Ireland at Twickenham saw them finish fifth.
Joe Schmidt's men had already wrapped up the title after England were beaten in both Scotland and France, and Saturday's loss put Eddie Jones' side on their worst run of results in the competition since 2006.
England had been pre-tournament favourites after Jones transformed a side who were humiliated on home soil at the 2015 Rugby World Cup, losing only one Test under the Australian prior to their recent slump – a run that included two Six Nations triumphs.
Haskell said the margins between success and failure in rugby can be minimal, but admitted England have not produced the performances to put themselves on the right side of that line of late.
"It happens in professional sport. The margins are very small. I'm not making excuses, but it is," he said.
"The difference between getting a result where everyone's blowing smoke up your bum versus disappointment.
"Today we were off. We were off last week and we're just not good enough at the moment. That's the difference. We've got to go away and work very hard.
