Christian Tello's first-half goal has put Porto on course to beat Maccabi Tel Aviv and move a step closer to the last 16 of the Champions League.
The hosts, who knocked out Basel on away goals to reach the group phase but have failed to score in their first three games, almost took an early lead when Eran Zahavi played a slide-rule pass into the path of Tal Ben Haim II, only to send his shot into the side-netting.
Within moments, Zahavi was again baring down on goal and the midfielder tried to cut inside to shoot, but was dispossessed by Ivan Marcano.
Having soaked up early pressure, Julen Lopetegui's men came close to taking the lead after Ruben Neves fed Vincent Aboubakar, who turned his marked and unleashed a fierce strike, which was met by a flying stop from Predrag Rajkovic.
On 12 minutes, Miguel Layun brought another save out of Rajkovic, but the Serbian could only parry the ball into the path of Aboubakar, who duly missed from close range.
As the game continued at a frenetic pace, Iker Casillas needed to be alert as Ben Haim II's shot was tipped away from danger.
The visitors finally broke through when Tello beat the onrushing Rajkovic with a controlled finish.
However, Porto came close to doubling their lead before half time as Aboubakar fired a shot off-target before Tello saw his effort turned over the bar by Tal Ben Haim I.
