Didier Drogba made a first appearance since re-signing for Chelsea but his side lost 3-0 to Werder Bremen in Germany.
Goalkeeper Thibaut Courtois made his Blues’ debut at the Weserstadion.
The 22-year-old Belgian joined Chelsea in 2011 but has spent the past three seasons on loan at Atletico Madrid.
Penalties from Eljero Elia and Felix Kroos and a header from Ludovic Obraniak gave the Bundesliga side the win.
The home side were awarded a penalty for a John Terry handball and went ahead when Elia scored from the spot.
Elia then picked out the unmarked Obraniak and he headed past Courtois to make it 2-0 before half-time.
Chelsea manager Jose Mourinho brought Drogba on for the second half, the Ivorian’s first outing for Chelsea since their Champions League triumph over Bayern Munich in 2012.
Eden Hazard and John Obi Mikel also played their first minutes of pre-season, with Petr Cech replacing Courtois in goal for the second half.
Kroos rounded off the victory on 89 minutes, converting from the spot after Nathan Ake had given away a penalty.
Werder Bremen : Wolf, Garcia, Caldirola, Galvez, Lukimya, Obraniak, Fritz, Di Santo, Elia, Junuzovic, Bartels.
Substitutes: Strebinger, Husic, Makiadi, Ekici, Hajrovic, Kroos, Kobylanski, Aycicek.
Chelsea: Courtois, Azpi, Zouma, Terry, Luis, Van Ginkel, Matic, Salah, Fabregas, Torres, Costa.
Subs: Cech, Ivanovic, Ake, Hazard, Mikel, Drogba, Cahill, Chalobah, Baker, Christensen, Boga, Solanke.