Chelsea suffered a damaging 3-0 defeat against Sheffield United at Bramall Lane, as their top-four hopes were dented heavily after the unexpected result. The Blues fell behind within the first 20 minutes, as the home side piled on the pressure and broke the deadlock.
David McGoldrick slotted past Kepa Arrizabalaga from close range after a deflection had floored the Spanish goalkeeper.
As Frank Lampard side threatened to peg back, Oliver McBurnie doubled the home side's advantage with a superb header. The Blues were left starring down the barrel and went into the interval two goals behind.
The Englishman made three substitutes in the second half to turn the game around, as the likes of Olivier Giroud, Marcos Alonso and Antonio Rudiger were introduced after the interval.
McGoldrick added a third in the 77th minute to put the game to bed after Antonio Rudiger made a poor attempt to clear the ball. Chris Wilder's side held on for a historic victory and cemented their hopes of securing European football.
The Blues are currently fourth on the league standings but could drop out of the top four if results don't go their way in the coming days.
Manchester United and Leicester City can leapfrog the Blues with a positive result and the top four race looks set to go down to the wire this season.