A spirited second half fightback wasn't enough for the Development Squad as they lost 6-3 against a strong Dagenham and Redbridge side.
The Hammers went behind in the third minute when Jake Larkins was unable to keep out Dwight Gayle's point-blank header, and despite reacting well it was soon two as Gayle caught them on the break and finished well.
Ian Hendon's side were to endure more bad luck before the halfway stage as the home side got their third when Gayle's tame shot took a wicked deflection rendering Larkins helpless.
The tide turned in the second half and the Hammers reduced the deficit after just one minute when Rob Hall was brought down and captain Jordan Spence hammered the spot-kick home.
Hall took centre-stage once more just two minutes later, drifting in from the right before bending a delicious ball inside the far post to make it 3-2.
On another day the Hammers would have completed their comeback and gone on to win and they almost equalised when Kenzer Lee's header was somehow tipped over as the away side continued to press.
Despite the Hammers' pressure, it was Dagenham's day as they struck twice on the counter-attack in quick succession - the goals coming from Billy Bingham and Jake Reed.
Sam Williams added a sixth before Jordan Spence converted from the spot for the second time before Sam Baldock and Frederic Piquionne were denied opportunities to further reduce the deficit.
Hendon accepted that his side should have shown more focus, particularly in the first half, but praised the effort of lone striker Paul McCallum.
"It was men against boys today, which is not necessarily a criticism as Dagenham are a very experienced, well-drilled side," said Hendon. "That said, we didn't dominate the midfield like we needed to and support Paul who showed a superb work-rate. He battled well against two big centre-halves and deserves a lot of credit."
Hendon also believes that positives can be taken in defeat. The Development Squad host Reading to begin their Barclays Under-21 Premier League campaign at Rush Green Stadium on Friday at 7pm, and he believes this result could provide the focus they need.
"We arrange these games with fitness and preparation being our main focus. Now we need to work hard to improve for Friday. They're all good players, but when it's tough like Saturday and we're up against it they need to show for the ball and want it more. That way we will create more and control the game."
Hendon bemoaned his side's lack of luck as the Daggers scored two goals from cruel deflections either side of the half-time break.
"I've seen a lot of positive signs in the past few games that suggest we have turned a corner. We have looked stronger, sharper and fitter. Maybe today is one of those days where things just haven't gone our way. We started the second half very well, got back into it, and then they scored via a deflection for the second time.
"We can count ourselves very unlucky."