A second-half goal from Joao Moutinho gave Porto a 1-0 win over Malaga on Tuesday in the last 16 of the Champions League, ending the Spanish club's unbeaten run in the competition and giving the Portuguese team a slender advantage for the return leg next month.
After almost an hour of sustained pressure, Porto's breakthrough came when defender Alex Sandro ran at the visitor's defense on the left flank and poked a pass through for Portugal midfielder Moutinho to side-foot the ball between Malaga goalkeeper Willy's legs.
In the other last 16 game taking place Tuesday, Bayern Munich beat Arsenal 3-1 in London.
The Iberian duel in northern Portugal produced a tight game with few clear goalscoring chances.
Porto, a two-time European champion in the knockout round for the seventh time in 10 years, was the hungriest team and mostly dictated the run of play.
Malaga, making its debut in the top-tier European competition and playing in Portugal after surprisingly winning its group earlier in the tournament, was happy to keep possession and cautious in attack as it held out for better chances in southern Spain.
"We were dominant, we pressured, we didn't let them play their game,'' Porto coach Vitor Pereira said. "It's just a shame we didn't get a second goal.''
Malaga had previously lost only once in 12 games on the road in Europe - a defeat that also came in Porto, against the city's second club Boavista, in the UEFA Cup during the 2002-03 season.
Porto came out fighting, with Marat Izmailov producing a low drive in the fourth minute that had Willy diving sharply to his left and central defender Fernando at the back post almost connecting with Silvestre Varela's flicked header in the 18th.
Jackson Martinez was guilty of squandering Porto's best chances. The Colombian striker, who is the Portuguese league's top scorer this season with 20 goals in 19 games, was denied from short range by Sergio Sanchez in the 32nd minute and then failed to control the ball inside the Malaga area five minutes later.
Sanchez threatened down the right flank in the 50th before Sandro blocked his pass inside the Porto area, but Izmailov soon came closer when his miscued shot at the back post bounced just wide of the post.
Moutinho broke the deadlock in the 56th.
Porto heaped pressure on the Malaga defense which held firm ahead of the March 13 decider.