Chelsea have fallen to third place in Group G after they suffered a 2-1 defeat to Porto at the Estadio do Dragao.
It took just two minutes for Porto's Yacine Brahimi to force an early save out of Asmir Begovic in the Chelsea goal, but up the other end, Cesc Fabregas saw Iker Casillas react sharply to push his strike past the post.
Shortly before the quarter-hour mark, the Blues should have edged in front after Diego Costa and Willian combined to set up Pedro, but the Spaniard was unable to test Casillas despite finding himself in a promising position.
Clear-cut opportunities were few and far between as the game progressed past 30 minutes, but Vincent Aboubakar did manage to get a shot away as he curled the ball just over the crossbar.
However, with six minutes of the half remaining, Andre gave the home side the lead when he was well placed to score after Begovic had initially saved from Brahimi.
Chelsea hit back two minutes into added-on time when Willian curled the ball past Casillas from a free kick to allow Jose Mourinho's men to go into the break on level terms, but seven minutes after the restart, they fell behind for a second time.
Maicon was the man who got it, heading in at the near post after evading the Chelsea defence, and it left the Blues with an uphill task for the remainder of the match.
They were almost level two minutes later, though, as Costa curled the ball towards the top corner but to the dismay of the striker, his shot struck the crossbar and bounced clear.
Mourinho threw on Eden Hazard, but it was Porto who spent the following 10 minutes in the ascendancy, as Giannelli Imbula, Danilo and Brahimi all threatened a third, and potentially decisive, goal.
However, with 16 minutes remaining on the clock, Chelsea should have equalised when Branislav Ivanovic met a corner, but the Serbian could only send his header wide of the target.
As full time edged ever closer, Danilo hit the woodwork with a header, but it proved irrelevant as the Portuguese giants held on to inflict another blow to Chelsea since the start of the campaign.