Chelsea boss Antonio Conte said referee Andre Marriner made a "bad decision" by not penalising Leroy Fer in the build-up to Swansea's second goal at the Liberty Stadium on Sunday.
Diego Costa handed Chelsea the lead in the 18th minute but two goals in the space of two minutes gave Swansea second-half advantage.
Gylfi Sigurdsson scored from the spot after being brought down by Thibaut Courtois before Leroy Fer dispossessed Gary Cahill to put the Swans ahead.
But Conte, whose side rescued a point when Costa struck nine minutes from time, thought Cahill was fouled by Fer for Swansea's second.
"The second goal I think everyone can see the situation," Conte told Sky Sports. "I don't want to speak about the decision but it's a bad decision from the referee.
"We conceded two goals, one after our own free-kick. We can improve on these situations."
Costa continued his excellent start to the season, scoring his third and fourth goals of the campaign to help his side seal a point.
And the former Juventus boss praised the Spain international's patience following his two-goal display at the Liberty Stadium.
"After all the games you asked me about the patience of Diego Costa and I'm very happy about his patience," Conte added.
"But I can tell you from the 1st minute to the 94th minute he took a lot of kicks. It's incredible that the defender finished the match."
Despite rescuing a point with just nine minutes remaining, Conte admitted he was disappointed with the result, claiming it is two points dropped for his side.
"It's a bit difficult to talk about the game because we dropped two points," Conte said. "We were dominating the game, leading 1-0 and creating a lot of chances to score the second and third goals. But in two minutes the match has changed.
"We did very well to eventually draw and even have chances to win the game. It's a pity because when you the opportunities to kill the game you must kill the game. This is the English league though and we know we've dropped two points.
"We are disappointed for the result but not the performance. The team created a lot of chances playing good football with a good intensity. When you have a lot of attempts you must score more goals to win."