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Thomas Tuchel's men came into the contest on the back of an embarrassing defeat to struggling West Brom but managed to put that behind them on Thursday (AEST), even if it was not entirely impressive.
Back on the scene of its 4-0 group-stage win over Sevilla due to coronavirus travel restrictions, Chelsea was second best for significant parts of the game but opened the scoring through Mount just past the half-hour mark.
Porto, without key men Sergio Oliveira and Mehdi Taremi due to suspension, were unable to apply the required finishing touch to some of their eye-catching build-up play and a defensive error gifted Chilwell the opportunity to seal what looks like a commanding first-leg advantage.
For all the talk of Porto representing a dream draw for Chelsea, it was Sergio Conceicao's men who looked brighter in the early exchanges, with Luis Diaz having an effort crucially blocked a few moments before Matheus Uribe saw a fine volley land on the roof of the net rather than in it.
Chelsea had another escape in the 24th minute as Edouard Mendy just about managed to stop Otavio scoring direct from a corner and Zaidu Sanusi put the rebound over.
But a period of Chelsea pressure followed and they capitalised, Mount producing a gorgeous turn to beat Chancel Mbemba on the edge of the box before firing into the bottom-left corner.
Porto began the second period encouragingly as well, Diaz seeing a curling effort go agonisingly wide from 20 yards after excellent work from Wilson Manafa.
An effort from distance at the other end – courtesy of Antonio Rudiger – led to Agustin Marchesin spilling at the feet of Timo Werner, who squared to Kai Havertz and he missed an open goal, though his blushes were spared, to a certain extent, by the offside flag going up against his compatriot.
Not that Chelsea were made to rue that situation as, soon after Christian Pulisic had hit the post on the break, Chilwell made sure of the victory as he pounced on a loose touch by Jesus Corona and tucked into an empty net after rounding Marchesin.