Romelu Lukaku was decisive off the bench with a late winner as Inter scraped a 1-0 victory over Porto in the first leg of their Champions League last-16 tie at San Siro.
Simone Inzaghi's men appeared to be heading for a disappointing goalless draw that would have arguably put Porto in the driving seat for the second leg, but Lukaku came to Inter's rescue.
The Nerazzurri had been wasteful during a tense first half, with Lautaro Martinez spurning a great opportunity and Alessandro Bastoni forcing Diogo Costa into a brilliant save.
They then struggled to make the most of their dominance in the second half, but shortly after Porto midfielder Otavio was sent off, Lukaku turned home to score for the second time in less than a week.
Martinez would have been frustrated to miss the target with an unchallenged header from Federico Dimarco's 13th-minute cross.
That chance punctuated the largely dull early exchanges, but the contest showed signs of life in the final eight minutes of the half.
Marko Grujic's fierce strike hit Andre Onana's knee and Galeno nodded the follow-up wide, before a remarkable reflex save from Costa kept Bastoni's header out.
Inter then owed a debt of gratitude to Onana just before the hour. He made a fine save to deny Zaidu Sanusi and then somehow kept Mehdi Taremi's rebound out on the line with the Iranian seemingly destined to score.
Otavio's dismissal for a lunge on Hakan Calhanoglu 12 minutes from time gave Inter a numerical advantage, and they duly made the most of it.
Substitute Lukaku headed Nicolo Barella's cross against the post but was on hand to slam the rebound beyond Costa.