But manager Alan Pardew cannot be expected to put the defensive problems right on the training ground, for three of the four goals conceded were the result of schoolboy errors, poor individual mistakes and bad decision-making by the players culpable.
To add further insult to injury, Jermain Defoe was sent off in the dying seconds of the first half for a late, lunging challenge and will miss the next four matches.
Yet Defoe had got Hammers off to a flier by scoring, courtesy of a near-post deflection, only 41 seconds after kick-off. His direct run on the left-hand edge of the area saw him reach the by-line, where his cross-cum-shot was diverted into the net at the Centenary Stand end.
Nine minutes gone and Brian Deane capped his home debut with a goal scored with a first-time left foot shot after good work by Don Hutchison, playing right midfield but popping up to provide from the left.
West Ham were in dreamland 11 minutes later when an audacious chipped free-kick from Defoe found the head of the unmarked Deane, who nodded the ball backwards into the net from six yards out.
And when Defoe again broke loose on the left to latch onto Hutchison's diagonal pass, it could have been 4-0 inside 20 minutes but for a low diving save by Albion keeper Hoult. The visiting manager was apoplectic with rage, while Pardew should have been banking on his first win as boss.
But after Koumas shot wide in the fourth minute, Albion managed only two more efforts on goal in the first half - and both led to goals.
Hammers'defensive horrors began after 25 minutes, when a misunderstanding between Christian Dailly, trying to shepherd the ball back to David James, and the hesitant keeper allowed Rob Hulse to steal in and prod the ball home from eight yards.
In the 40th minute, Hulse easily shrugged off Dailly, turned and unleashed a fine shot into the roof of the net from the edge of the area as Albion cut the deficit to 3-2.
It got worse in time added on at the end of the first half when Defoe, having earlier been harshly booked for diving, was shown a straight red card for a late challenge on Gregan as the defender cleared the ball on the edge of his own area. Having been sent off at Gillingham in September, Defoe now misses the forthcoming league games against Watford, Wimbledon, Wigan and the return with West Brom.
Not that being reduced to 10 men should excuse the manner of this defeat. West Ham still held the lead at half-time but, with Deane alone upfront, the visitors enjoyed increased possession and in the 65th minute they got another lucky break.
Deane needed one for a dream debut hat-trick but his goal came, agonisingly, at the other end when he sliced a left-wing corner into his own net from six yards.
West Brom couldn't believe their good fortune again on 76 minutes. James, inexplicably rushing from his line to punch a high ball, miscued his attempted clearance straight to the feet of sub Hughes, who directed the ball back into the empty net.
Robert Lee came on for Wayne Quinn, allowing Hutch to join Deane in attack, but Hammers didn't look like grabbing an equaliser. The fans, who had been behind their team and sparked the best atmosphere seen at the Boleyn this season, rightly felt badly let down and many left early to reflect on an amazing afternoon to forget.
Alan Pardew didn't try to excuse his players' ineptitude afterwards. He said: "We were terrific in the first period of the opening half and things were going smoothly. But we started to get carried away with ourselves and got a knock-back.
"I was looking for leadership, for people to show some character and roll up their sleeves, but the second half was something I've not experienced before. I'll look back on this game and not forget it. And I'll not let the players forget it either. We've got Premiership class players out there and I expect better. There were players who were in a relegated side last season and it showed. We need to eradicate that double lively.
"If there was a positive out there today, it was the way we played in the first period. All we needed to do after that, even once we were down to 10 men, is keep the ball, in the culture of the club, but we didn't do it."
Pardew didn't lay any blame at the feet of Defoe, though, and in fact defended the striker when he added: 'His first booking was particulary harsh, he wasn't even looking for a penalty. The second one was a bit of fast, quick challenge and his exhuberance got the better of him. But it was a genuine attempt to get the ball and he was very unlucky to be sent off. I don't even think he caught the player, whose reaction to the challenge didn't help."
Pardew made it clear he will be expecting a positive response from his players to this bizarre defeat. He says: "I can promise West Ham fans that I won't let my head go down after what I've seen today, and I'm learning about the strengths and weaknesses of my players in every match.. I'll be there at training on Monday ready to work and I expect my players to be ready, too. On time."
by Tony McDonald