Mehdi Taremi scored a sensational bicycle kick in injury time to give Porto hope of levelling the tie, but Chelsea held on to win 2-1 on aggregate.
Thomas Tuchel’s Blues had won the ‘away’ leg of the quarter-final 2-0 in Seville last time out thanks to goals from Mason Mount and Ben Chilwell, leaving Porto with an uphill task in the return leg.
Porto put on a spirited display but lacked quality in the final third until the late goal. Had their players shown half as much conviction in attack as they did while hitting the turf trying to win free-kicks from referee Clement Turpin, the second leg could have been a different story altogether.
As it was, Tuchel could scarcely have wished for a more comfortable 90 minutes with which to seal a spot in the last four of the competition – but Taremi’s late goal made them sweat.
Chelsea were content to cede possession to their opponents and, given Porto’s lack of bite in attack, the Blues didn’t have to get out of second gear to reach the semi-finals. Taremi came off the bench to force a save from Mendy with 25 minutes remaining, but Chelsea heeded that warning and tightened up.
Christian Pulisic wasted a late chance to seal the tie, and Taremi’s incredible volley deep into injury time set up a tense finale – but it was too little, too late for them.
Tuchel can now prepare for this weekend’s FA Cup semi-final against Manchester City at Wembley, while Chelsea can also look forward to a Champions League semi-final against either Real Madrid or Liverpool later this month.