Graeme Souness felt a victory like this had been coming for his neat and industrious side, but he must still have been surprised to see his players speed into a three-goal lead before half an hour had elapsed.
Until Garry Flitcroft headed in Corrado Grabbi's clever centre, West Ham had actually acquitted themselves quite well but that 18th-minute breakthrough was the catalyst for the most abject surrender imaginable.
Nine minutes later David Dunn had embarrassed Shaka Hislop with an exquisite shot from 30 yards that caught the goalkeeper slightly off his line, and within another 60 seconds, Tugay Kerimoglu's cross was headed across goal by Grabbi for Damien Johnson to make it 3-0 from point-blank range.
Briefly, West Ham rallied. A low 20-yard drive by Michael Carrick offered a glimmer of salvation but when Sinclair squandered a fine chance to make it 3-2 four minutes into a tetchy second half they crumbled again.
Repka was dismissed just after the hour after taking Grabbi's heels for an innocuous second booking and when the substitute Grant McCann sliced Tugay's cross into his own net a couple of minutes later it was damage limitation time.
Or at least it should have been. A thumping right-foot drive from Tugay narrowly beat Dunn's effort as the game's outstanding moment. Jansen lashed in the rebound after Hislop failed to hold Dunn's drive and, after seeing how easy it was, the substitute Craig Hignett weighed in with the seventh from a Jansen cross. Blackburn were awesome.
"There is going to be a lot of soul-searching in the next few days," said West Ham boss Glenn Roeder.
"There were players out there who can do better and players who were doing their best but can't do any better. Our squad is at least four or five people short. It hurts. I hope I get more time but whether it's me or ultimately someone else, who knows?
"I know that whoever it is, they won't have a magic wand to turn things around immediately.
"There isn't much money to spend and if we keep defending like this we are going to be in serious trouble."
West Ham's position in the relegation quicksand is not a false one
Guardian Service
BLACKBURN: Friedel; Neill, Berg (Short 71), Johansson, Bjornebye, Johnson (Hignett 75), Flitcroft, Tugay, Dunn, Jansen, Grabbi (Hughes 76). Subs Not Used: Mahon, Kelly. Booked: Grabbi. Goals: Flitcroft 18, Dunn 27, Johnson 28, McCann 63 og, Tugay 80, Jansen 82, Hignett 90.
WEST HAM: Hislop; Schemmel, Dailly (Foxe 45), Repka, Soma, Sinclair, Hutchison, Carrick, Moncur (McCann 45), Kanoute, Di Canio. Subs Not Used: Kitson, Defoe, Bywater. Sent Off: Repka (61). Booked: Moncur, Repka, Kanoute, Di Canio. Goals: Carrick 39.
Referee: A D'Urso (Billericay).
