Chelsea must wait to secure qualification from Champions League Group G after Eden Hazard missed a late penalty in a 1-1 draw against minnows Maribor.
The Slovenians were unrecognisable from the side beaten 6-0 by Chelsea two weeks ago and claimed a deserved lead when Agim Ibraimi curled in a beautiful shot into the top corner five minutes into the second half.
Chelsea boss Jose Mourinho had already reacted to a poor first-half showing by his side at the Stadion Ljudski vrt by making a double substitution at half-time, introducing striker Diego Costa and Oscar.
Luka Zahovic missed a fine chance to double the advantage and enhance Maribor's claims of inflicting Chelsea's first defeat of the season, before Nemanja Matic's close-range effort 17 minutes from time which saved the Blues' blushes.
Maribor goalkeeper Jasmin Handanovic saved well from Hazard and Costa, who had the ball in the net after 79 minutes, only for the strike to be ruled out for offside. Hazard was then fouled for an 86th minute spot-kick, but the Belgian's effort was too central and Handanovic saved.
Mourinho was less than impressed by the performances against Shrewsbury and QPR and it was another insipid showing.
It was not the warm-up the Premier League leaders would have been hoping for ahead of a return to domestic duty at Liverpool on Saturday lunchtime.
While Liverpool made wholesale changes for their Tuesday night trip to European champions Real Madrid, Mourinho kept his to four for a match against a team merely pleased to have reached this stage.
Petr Cech made his fourth start of the season after being displaced by Thibaut Courtois as first-choice goalkeeper. Kurt Zouma, Didier Drogba and Andre Schurrle also came in following the 2-1 defeat of QPR, for Gary Cahill, Costa and Oscar.
Zouma could have given the Blues, playing in yellow, the lead but headed wide from Fabregas' cross after Maribor half-cleared a corner. A deflected Drogba shot was saved by Handanovic as Chelsea pressed forwards again, with Maribor packing bodies behind the ball and playing on the break.
Maribor breached the Chelsea defence, but Zouma scrambled clear a Sintayehu Sallalich shot after Zahovic's pull-back.
World Cup winner Schurrle has struggled to impress since returning to club duty, missing a host of chances against Bolton, spurning a sitter at Sporting Lisbon and doing little to enhance his hopes of regular game time at Shrewsbury last week.