A stirring display from West Brom saw them inflict a first Premier League defeat since New Year’s Day on Chelsea as the champions were brought crashing back down to earth following Saido Berahino’s brace - taking his tally to 20 for the campaign - and a Chris Brunt strike.
Yet it was the bizarre sending of off Cesc Fabregas for which this contest will be ultimately remembered.
With play stopped, the Spain international kicked the ball into a crowd of players - still tussling after Diego Costa and Gareth McAuley had clashed - and struck Brunt on the head.
The repercussions of that moment of madness are set to be felt next season too, with Fabregas’ three-game ban due to run into the start of next season.
Callum McManaman fired out an early warning sign within five minutes when he got the better of Filipe Luis before flashing a shot goalwards from an acute angle which Thibaut Courtois did well to divert away for a corner.
The Belgium international had no answer to Berahino’s brilliance four minutes later, however, as the Baggies forward ended a nine-match goal drought.
West Brom boss Tony Pulis had expressed fears that Berahino was suffering from “burnout” ahead of the game.
Yet, after controlling Joleon Lescott’s sideways pass 20 yards out, there was nothing sluggish about his finish as he whipped a wonderful arcing shot inside the right upright.
No player has contributed more to Albion surviving this season but, with the goals having dried up of late, it remained a timely reminder of the 21-year-old’s potent predatory instincts - one unlikely to have gone unnoticed by what is expected to be a string of summer suitors.
Then came the controversy.
Costa and McAuley clashed inside the Albion area off the ball, prompting a player melee which culminated in the Chelsea forward being cautioned.
That, however, was just the start of the drama.
Mindlessly, Fabregas, around 20 yards away from the cluster of warring players, when he booted the ball into their direction and hit Brunt plumb on the head. It was an act of gross stupidity from the Spaniard and, after receiving a furious shove from Fletcher, he received his marching orders from referee Mike Jones.
Albion almost doubled their advantage just before the interval when James Morrison fed Chris Brunt only for Courtois to be smartly off his line to save .
Jose Mourinho having a pre-match kickabout with a West Brom mascot tonight. Nice touch. pic.twitter.com/3EUGleRbtn— Squawka Football (@Squawka) May 18, 2015
Yet within two minutes of the restart they were celebrating again.
Once again, Berahino was the thorn in Chelsea’s side, turning sharply to outfox Gary Cahill before being sent tumbling inside the penalty area after being clearly caught by John Terry.
There could be no arguments over Jones’ decision to point to the spot, however Chelsea’s captain, having been the last man, could count himself somewhat fortunate to escape without sanction. Berahino dusted himself down before lashing his penalty into the right corner. Courtois guessed correctly but the shot just had too much venom.
The 57th minute provided a further suggestion it was not to be Chelsea’s night as Loic Remy, having masterfully side-stepped Claudio Yacob, cracked a shot against the inside of the left post before the ball was scrambled to safety.
It went from bad to worse for Chelsea on the hour mark.
A quickly-taken short corner between Brunt and substitute Craig Gardner handed the Northern Ireland international a sight of goal and his driven shot squirmed agonisingly underneath Courtois to beat the goalkeeper at his near post.
Myhill 7; Dawson 8, McAuley 8, Olsson 7, Lescott 7; McManaman 7, (Gardner 54, 7) Fletcher 8, Yacob 8, Morrison 8 (Baird 89), Brunt 8; Berahino 9 (Ideye 79).
Rose, Wisdom, Baird, Mulumbu, Anichebe.
Olsson, Fletcher, Gardner
Courtois 5; Ivanovic 4, Cahill 5, Terry 5, Filipe Luis 4; Loftus-Cheek 5 (Ake 73), Matic 5; Remy 6 (Brown 79), Fabregas 3, Hazard 4; Costa 5 (Cuadrado 64, 5).
Blackman, Christensen, Azpilicueta, Mikel, Cuadrado.
Mike Jones (Cheshire)