Mount's slick turn and shot in the first half would have been painful enough for Porto, who were the better side for large spells of this first leg in Seville but repeatedly lacked the precision to take advantage. Instead, their misery was compounded by Ben Chilwell capitalising on a mistake at the back to score a late second that gave Chelsea another away goal and leaves them on the brink of the semi-finals.
They were away goals only in name given both these teams were playing in the unfamiliar Ramon Sanchez Pizjuan, where they will meet again next week, just with the home and away roles reversed.
Porto were in the home dug-out, wore their home kit, had a large club banner in the empty stand behind one goal. And Chelsea played the part too hitting their opponents on the counter-attack, their quality in the final third proving decisive.