Diego Costa latched onto a Cesc Fabregas through-ball and powered his shot past the Olimpija keeper
Cesc Fabregas set up fellow debutant Diego Costa to score as Chelsea beat Olimpija Ljubljana 2-1 in Slovenia.
The Blues had trailed at half-time to a Darijan Matic strike in front of 16,000 inside the Stozice Stadium.
But the Spain team-mates combined for Chelsea's equaliser after 55 minutes, before Kurt Zouma prodded in a rebound eight minutes later.
Boss Jose Mourinho said: "We feel we are going to be very strong and we want to fight for the title."
The match also featured an terrible miss from Fernando Torres, who chested a Nathan Ake cross over the bar from two yards out, with the goal gaping.
New signing Didier Drogba, in his second spell at the club, did not feature, but watched on from the sidelines.