West Bromwich Albion took advantage of a howler from Sunderland goalkeeper Simon Mignolet to move up to third place in the Premier League with a 4-2 win at the Stadium of Light on Saturday.
Steve Clarke's side were leading through Zoltan Gera's blistering first half strike when Mignolet allowed the ball to slip from his grasp and Shane Long tapped in to cement Albion's lead.
Craig Gardner got one back for Sunderland in the second half before a penalty from Albion forward Romelu Lukaku.
Stephane Sessegnon struck late for the hosts, but Marc-Antoine Fortune sealed the Baggies' fourth successive win in stoppage time.
West Brom's victory lifted the season's surprise package above Chelsea and within two points of leaders Manchester City, while Sunderland lie only three points above the relegation zone.
Black Cats defender John O'Shea, who had already been booked, was involved in an early flashpoint when he challenged Long just outside the Sunderland penalty area.
Initially it seemed Mike Dean was about to show the former Manchester United star a second yellow card, but instead the referee booked Long for diving.
Albion snatched the lead against the run of play in the 30th minute when Gera pounced on Adam Johnson's poor control 25 yards from goal and unleashed a superb shot that had too much power and movement for Mignolet to keep out.
Martin O'Neill's side suffered a blow when midfielder Lee Cattermole was forced off with an injury. And it got worse for Sunderland when Mignolet's blunder gifted Albion their second goal in the 44th minute.
Chris Brunt's over-hit through pass should have been easy for Mignolet to collect, but the Belgian somehow let the ball escape and Long was on hand to pounce as the Irish striker slotted into the empty net.
Mignolet was more secure when Brunt slipped Long clear in the second half, this time the 'keeper was off his line to block the striker's shot.
Gardner reduced the deficit in the 73rd minute when his free-kick took a deflection off Fortune in the defensive wall and looped into the net.
But Johnson's rash lunge on Liam Ridgewell in the 81st minute conceded a penalty that on-loan Chelsea forward Lukaku calmly converted.
Sessegnon then fired home from close-range after Steven Fletcher's header was saved in the 87th minute, but Albion substitute Fortune netted on the counter-attack with virtually the last kick of the match.