Leroy Fer appeared to foul Gary Cahill before scoring Swansea's second goal and Cesar Azpilicueta was frustrated the referee missed it.
Cesar Azpilicueta felt referee Andre Marriner missed a "clear foul" on Gary Cahill in the build-up to Leroy Fer's goal as Chelsea were held to a 2-2 draw by Swansea City at the Liberty Stadium.
Chelsea led at half-time following Diego Costa's opening strike, but two efforts in the space of three second-half minutes saw Swansea take the lead.
Gylfi Sigurdsson slotted home a penalty after he was felled in the box by Thibaut Courtois following a break, before Fer dispossessed Cahill and produced a shot that squirmed beyond the goalkeeper.