Chelsea were left waiting for their place in the last 16 of the Champions League after coming from behind to draw 1-1 away to Maribor on Wednesday.
Jose Mourinho's side then squandered a gilt-edged chance of victory when Eden Hazard missed a penalty.
Premier League leaders Chelsea, who only a fortnight earlier thrashed Maribor 6-0 at Stamford Bridge, fell behind to Agim Ibraimi's 50th-minute goal in this Group G clash.
The hosts should have gone 2-0 up but Luka Zahovic somehow contrived to miss an open goal as the game entered its final 20 minutes and were made to pay as Nemanja Matic equalised to spare the blushes of Mourinho's team.
Chelsea then missed several chances before Hazard won a penalty with five minutes remaining after being brought down in the box by Mitja Viler.
Hazard took the penalty himself but impressive goalkeeper Jasmin Handanovic dived to his left to save the spot-kick.
"The first half we were poor, in the second half after their goal we played very well and normally we should win the game but when you don't play well for 90 minutes you risk," Mourinho said.
"In the last 30 minutes when we played really well, intense and creative and had a big desire to win we had lots of chances to do it, their goalkeeper was magnificent."
Meanwhile the Portuguese boss absolved Hazard of blame for the loss, saying he had been "absolutely fantastic" and the "best player of my team".
Maribor coach Ante Simundza said he was proud of his team's performance in front of a passionate home crowd.
"We showed our character," he said. "With some luck we could have won, with some bad luck we could loose.
"The biggest difference compared to the match we lost in London 6-0 was that Chelsea then hit from every chance, this time with he help of our home crowd it was different."
Ibraimi's curling shot from the edge of the box had given Maribor the lead but Matic drew Chelsea level when he struck from close range following a corner.
Chelsea could have won the match late on but Handanovic made excellent saves to deny both Hazard and Diego Costa.
Had Chelsea -- the 2012 Champions League winners -- beaten Maribor and other results gone their way, they would have qualified for the last 16 of this season's competition with two games to spare.
- Fake situation -
In the build-up to this match, Mourinho had been at pains to label Chelsea's 6-0 home win a "fake situation", saying he knew Maribor were a "good team".
Kurt Zouma could have given the visitors the lead but headed wide from a Cesc Fabregas corner.
But Chelsea failed to get going in the first half and Mourinho responded by sending on Costa and Oscar after the break in place of Willian and Schurrle.
However, five minutes into the second period the visitors were behind after Chelsea, failing to clear the ball properly, saw Ibraimi beat Petr Cech with a superb curling shot into the far corner.
Ramires replaced Filipe Luis as Mourinho switched to three at the back.
But as Chelsea were adjusting to their new defensive formation, Viler sped forward and crossed to the back post, where Zahovic shot over the top when it seemed easier to score.
Oscar's deflected shot led to Chelsea's equaliser from the ensuing Fabregas corner, with John Terry heading the ball down for Matic to lash home.
Hazard should have made it 2-1 but was denied by Handanovic when one-on-one with the goalkeeper, who later tipped Costa's volley over the crossbar.