Academy Director Tony Carr admitted individual errors had cost West Ham United Under-18s dear in their 4-1 FA Premier Academy League defeat by Fulham on Saturday.
The Hammers created more than enough opportunities to take something from the game, only for a combination of poor finishing and defensive mistakes to send them spiralling to defeat.
Elliot Lee (pictured) netted his 13th goal in 17 appearances in league and cup, but it was a mere consolation as the Cottagers took all three points home from Little Heath.
Fulham took an early lead before Lee equalised from the penalty spot before half-time to continue his superb season, only for the visitors to re-take the lead before the interval. West Ham tried gamely to get back on level terms for a second time, only for two counter-attack goals to give the final scoreline a one-sided appearance.
"I cannot hide the fact that a couple of mistakes have cost us big-time," said Carr. "It sounds stupid but we should have won in terms of chances and possession.
"Our goalkeeper Sam Cowler had one of those days when his errors have cost us. He just had a bad day at the office. It was a defeat that was so disappointing and hard for all of us to swallow.
"We battered them through the whole second half and had chance after chance, but they broke off and scored their third and fourth goals."
The U18s will now take a three-week break from competitive action before travelling to Chelsea on Saturday 7 January 2012. The Hammers also have an FA Youth Cup fourth-round tie to look forward to, with Brighton and Hove Albion visiting the Boleyn Ground before Saturday 21 January.
West Ham United U18s: Cowler, Young, Shaw (Miles 80), Chambers, K.Lee, Turgott, Vose (Bunjaku 60), Ruddock, Powell, Fanimo (Sadlier 70), E.Lee