Chelsea have been held to a 1-1 draw by Red Bull Salzburg in Graham Potter's first game in charge of the Premier League club.
Raheem Sterling put the Blues ahead shortly after the break, but Noah Okafor netted 15 minutes from time to earn the Austrian outfit a point from the Champions League fixture at Stamford Bridge.
Chelsea remain at the bottom of Group E with just one point from their opening two continental fixtures, but only three points separates them to leaders and next opponents AC Milan.
Potter caused major surprises with his team news by dropping Wesley Fofana and Kalidou Koulibaly to the substitutes' bench, instead starting Cesar Azpilicueta alongside Thiago Silva in a back four.
However, the change in system did not harm the West Londoners as they had the better of the first half without overwhelming threatening an opener.
As well as a couple of goalbound shots being blocked, Mason Mount sent an effort fizzing wide of the post, but the first goal of the Potter era arrived shortly after the break.
Reece James and Mount combined down the right before the latter's low cross found Sterling, who had time and space to find the far bottom corner from 14 yards.
Although the home side continued to have the better of the play, the visitors were always competitive, and they pounced as soon as Chelsea made a mistake at the back.
Thiago Silva failed to be decisive enough with a tackle out on the left, allowing Junior Adamu to deliver a low cross for Okafor's to send a deflected effort past Kepa Arrizabalaga from 10 yards out.
Potter had little intention to settle for a point, introducing attack-minded players and lining up with a back three consisting of James, Silva and Marc Cucurella.
The approach almost paid off when Armando Broja ran the length of the pitch to deliver a low cross for Hakim Ziyech, but goalkeeper Philipp Koln was able to make the block from close range.
Broja then squandered a chance to win it in added-on time, drilling a volley over the crossbar from eight yards when he should have scored, before Ziyech mistimed a more difficult chance into the grateful gloves of the Salzburg stopper.
