Porto 2 Chelsea 1
Chelsea’s woes continued with a Champions League defeat against boss Jose Mourinho’s former club.
Willian’s stunning free-kick seconds before the half-time whistle hauled the Blues level after Andre Andre had opened the scoring.
But Maicon restored Porto’s lead six minutes into the second half and Chelsea were unable to find an equaliser, with Diego Costa hitting the woodwork.
The result means that Chelsea, whose poor start to the campaign has left them 14th in the Premier League table, have lost four of their 10 matches in all competitions this season.
Their defensive shortcomings were evident again, not least in the build-up to the opening goal when Branislav Ivanovic, who has attracted criticism for his performances, was at fault once more.
Yacine Brahimi went past him, and Asmir Begovic produced a fine save to keep out the Algerian’s shot only for Andre to follow up to score.
Chelsea were the better side for much of the first half and deserved to end it on level terms.
But they switched off at a set-piece soon after the restart and Maicon got in front of Ramires at the near post to head Rúben Neves’ delivery past keeper Begovic.
Eden Hazard, who was left out of the starting line-up by Mourinho along with Nemanja Matic and John Terry, fired into the side-netting soon after coming on.
Costa, who was excellent up front, went closer to levelling when his dipping 25-yard effort from the left-hand side hit the bar.
And Ivanovic missed a great chance, heading wide of the target following an error by Porto keeper Iker Casillas.
At the other end, Chelsea continued to defend shoddily and almost conceded another goal from a near-post header from a corner, this time when Danilo hit the post.
There was drama late on, with Chelsea appealing in vain for a penalty after Ivan Marcano appeared to handle, and then, in the final seconds, when Costa fired narrowly wide.
Subs not used: Blackman, Baba Rahman, Terry, Loftus-Cheek.