Frederic Kanoute missed an open net for Sevilla moments before the winner was scored...
Rolando put the away side ahead in the second period, but Sevilla struck back through a Frederic Kanoute header just eight minutes later. But five minutes from time Fredy Guarin tapped home the winner.
Porto looked dangerous on the counter-attack especially through Hulk who ran straight at the heart of the Sevilla defence but was thwarted twice thanks to excellent recovery tackles from Gary Medel and Sergio Sanchez.
However the home side did come back into the match and thought they had a penalty as Luis Fabiano tumbled over in the box, but Rolando had made an excellent recovery tackle to poke the ball from the foot of the Brazilian.
Then moments later he bailed out his team-mate Nicolas Otamendi, who was brushed aside by Luis Fabiano but he could not find a way past the solid Rolando.
Rolando frustrated the Sevilla strike-force as he executed a stunning last ditch tackle on Kanoute on the edge of the six yard box after a low Luis Fabiano cross from the left.
The away side did have their chances as Andres Palop punched a corner out to a waiting James Rodriguez but Martin Caceres was on hand to acrobatically head the shot away. Varela was also a threat down the left but again Caceres was alert to the threat and closed him down well.
Sevilla were well on top at the start of the second half as Kanoute went close with a shot from the edge of the area after Ivan Rakitic broke well from midfield.
Tempers began to flare after a few strong tackles and completely against the run of play Porto broke the deadlock as Rolando directed home a James Rodriguez free kick, though he seemed to be a touch offside.
But only eight minutes later Rakitic floated in a free kick for Kanoute, who towered over Otamendi to head the ball home and level the match. Then straight after the restart a Luis Fabiano header forced a great save from Helton.
Kanoute then put in his contender for miss of the season. Alvaro Negredo headed the ball down for Kanoute who side footed back to his strike partner from four yards out instead of into an empty net.
Sevilla were then punished for not putting away their chances as Cristian Rodriguez broke through after a mistake by Federico Fazio, but after an initial save from Palop the ball fell into the path of Guarin who tapped into the empty net.
As a result the second leg in Portugal is sure to be a cracker.