The London rivals started the New Year’s Day showdown at Craven Cottage in the relegation zone and the match was poised at 1-1 when Kevin Nolan was sent off for West Ham, putting Fulham in the driving seat.
Mohamed Diame and Sidwell swapped goals before referee Mark Clattenburg showed team captain Nolan a red card for kicking Fernando Amorebieta two minutes before half-time.
And manager Sam Allardyce was quick to slate “irresponsible” Nolan, claiming he cost West Ham a priceless victory.
Allardyce said he will review Nolan’s captaincy, admitting he cannot fathom his long-term chief lieutenant’s recent behaviour.
“I just don’t quite understand where he’s lost his cool and why it’s happened,” said Allardyce.
“I know the centre-half fouled him, and I also know that (referee) Mark Clattenburg didn’t give a free kick and he should have done.
“But it’s still not an excuse for what Kevin did.”
Allardyce felt his side should have capitalised on their early advantage, and Nolan was again to blame.
“He was involved in a real key moment that was looking good for us in terms of the header on the far post that would have sent us 2-0 up,” he added.
“So he’s responsible for us probably losing the game more than anything else, there’s no doubt about that.
“And you can expect it from somebody starting out occasionally, a youngster finding his way in the game, finding out about the nitty-gritty of the Premier League.
“The pulls, the pinches, whatever they might be: but not Kevin.”
Yesterday’s defeat leaves West Ham locked in the relegation zone.
Allardyce said he will worry more about midfielder Mark Noble’s calf problem that could be a muscle tear, than Nolan’s predicament.
Fulham head coach Rene Meulensteen was proud of his players for attacking with purpose and incision after Nolan’s dismissal.
A week on from capitulating 6-0 at Hull, Meulensteen said this victory proves that hammering was not a trend to be overly worried about.
“The sending off helped us but we still had to be calm and attack with quality,” said Meulensteen.
FULHAM: Stockdale, Riether, Senderos, Amorebieta, Riise, Parker, Sidwell, Duff (Kasami 78),Taarabt (Bent 69), Richardson (Kacaniklic 56), Berbatov.
WEST HAM: Jaaskelainen, Demel, O’Brien, Diarra, McCartney, Diame (Downing 56), Noble (Rat 32), Collison, Nolan, Taylor, Maiga (Carlton Cole 69).
Referee: Mark Clattenburg.