Looking to level the tie, Die Schwaben came out quickly with Angelo Stiller’s set-pieces causing problems as Costa was forced to push a Jeff Chabot header over the crossbar before Chris Fuhrich fired an attempt over.
Deniz Undav then bent a shot wide from a Fuhrich pullback, and that wastefulness was punished by Porto in the 21st minute. Somewhat against the run of play, Borja Sainz’s determination was rewarded when the ball bounced off him from Atakan Karazor’s tackle and into William Gomes’ path for the midfielder to tap home.
Even with their lead extended, Porto had to battle to maintain it as they had three yellow cards by the half-hour mark.
The hosts still showed the potential to extend their buffer as Sainz broke forward again and found Zaidu Sanusi, whose shot was saved.
Costa was required to put in more impressive work to maintain it, as the Dragoes captain got down to tip Bilal El Khannouss’ strike wide before clawing away a Fuhrich attempt that had looked destined to curl into the top corner.
Sainz then fired wide with a shot of his own before Rodrigo Mora slid his effort agonisingly past the post.
It didn’t take long after the restart for Costa to catch the eye yet again, this time reacting superbly to tip Undav’s effort wide.
The goalkeeper wasn’t required when Maximilian Mittelstadt sent a tame shot trickling past the post, and when he was given a scare with Undav flicking the ball over him, the ball went wide as a goal continued to evade Die Schwaben despite the relentless pressure they were applying.
Porto made forays forward of their own and inflicted a devastating blow in the 72nd minute, as Victor Froholdt was dispossessed by Stiller but won the ball back from him and emphatically smashed it into the top corner.
Things soon got worse for the visitors, as Nikolas Nartey was sent off after receiving two yellow cards inside a minute, having only been on the pitch for 15 minutes.
Porto still didn’t let up at all to ensure a clean sheet accompanied the 11th win from their last 12 home games across all competitions, as they set up a contest against Nottingham Forest in the Dragoes’ first UEL quarter-final since 2013/14.
In contrast, Stuttgart have just one win from their last five away fixtures as they exit the competition.
Flashscore Man of the Match: Diogo Costa (Porto)
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