Ricardo Quaresma struck 15 minutes from time to lift Porto to a 2-1 win over Athletic Bilbao on Wednesday and put the hosts in command of UEFA Champions League Group H.
Mexican midfielder Hector Herrera had put the Portuguese side ahead at the Dragao stadium on the stroke of half-time before Athletic's Guillermo Fernandez equalised before the hour mark.
Substitute Quaresma then came to the rescue four minutes after entering the pitch, hitting the ball past a helpless Athletic goalkeeper Gorka Iraizoz to hand his team three valuable points.
The outcome has lifted Porto two points clear of Shakhtar Donetsk at the top of the pool, with seven points from their opening three games.
Athletic remain winless and with just one point so far, the Basque outfit's chances of progressing to the next round are slim.
The visitors went into the game looking to spark their season into life after a nightmare start in the Spanish league.
But Porto looked more dangerous from the start and first tested Iraizoz in the 17th minute when the Athletic keeper kept out Juan Quintero's powerful effort.
The home side wasted a good chance in the 39th minute when Cristian Tello fed Danilo in the area and his right-footed effort went just wide of the far post.
But Porto's efforts paid off before half-time when Quintero set up an unmarked Herrera in the box and his first-touch finish towards the far post beat Iraizoz.
Athletic coach Ernesto Valverde made a double substitution after the restart with Iker Muniain replacing Aritz Aduriz and Benat taking Mikel San Jose's place in midfield.
Porto had the first chance in the second half with Quintero's bullet strike from outside the area saved by Iraizoz.
At the other end, Markel Susaeta fed Guillermo on the right side of the area and his angled effort was kept out by Porto goalkeeper Fabiano.
The visitors continued to press forward and were rewarded in the 58th minute. Benat's pass found Guillermo in the box and he hit the ball towards the far post and out of Fabiano's reach.
Athletic's joy did not last long as Porto went in front for good via Quaresma. A poor clearance from Athletic's defence allowed the hosts to launch a counter-attack and Quaresma found space in the area and drilled a shot on target, with the ball going under the body of Iraizoz and into the back of the net.
Athletic could have claimed a point five minutes later but Aymeric Laporte's header from Benat's cross was kept out by Fabiano as Porot held on for the valuable win.