Diego Costa struck twice but errors from Thibaut Courtois and Gary Cahill cost Chelsea victory at Swansea but there appeared to be an injury to John Terry before the final whistle.
Diego Costa had fired the Blues into a first half lead but the Belgian goalkeeper stupidly hurled himself at Gylfi Sigurdsson in the penalty area to concede a spot kick that the Iceland international dispatched with aplomb.
And, just moments later, Cahill was caught in possession by Leroy Fer who raced in to slot the ball past Courtois.
The England defender cried foul but Andre Marriner rejected his appeals and, even then, his poor first touch invited the Dutchman into challenge. With hindsight, Cahill would have played the ball straight to Courtois.
Costa, who was his usual warrior self, equalised with an overhead kick that went in off the face of Stephen Kingsley.
After a quiet opening spell, Chelsea brought the game to life as Swansea failed to deal with a ball into the area. Willian fed Costa, who rifled the ball past Fabianski.
The Polish stopper made a fine save to deny the Brazilian soon after as the Blues started to dominate proceedings.
John Terry and Diego Costa should both have scored before the break but both elected to turn the ball across the face of goal.
The game changed just before the hour mark as Courtois needlessly raced out to launch into a tackle onto Sigurdsson and giving away a penalty.
The Iceland international dispathed it with aplomb and the Belgian was picking the ball out of his net three minutes later as Cahill was dispossessed by Fer who raced in to score.
Chelsea pushed forward looking for an equaliser and they got it when Costa's overhead kick went in off Kingsley.
In the dying seconds, Terry suffered an injury that had the Chelsea captain beating the pitch in frustration at the final whistle.