Porto oust Sevilla from Europa League
The Portuguese, who won 2-1 in Spain last week, went into the game having lost just once in 34 matches and dominated throughout with Brazil forward Hulk missing several chances and Colombia striker Radamel Falcao sending a header crashing against the bar.
But the hosts were stunned when their former player Luis Fabiano latched on to a pass from Alvaro Negredo to score with a clean finish on 71 minutes.
Just moments later, Porto suffered another blow when Uruguay left-back Alvaro Pereira received a straight red card for a foul on Gary Medel. Sevilla defender Alexis was also sent off for a second booking in the 75th minute.
With more room for the forwards, both sides came close to scoring in the closing stages.
Sevilla striker Frederic Kanoute headed just wide and Porto forced keeper Javi Varas to make several fine saves.
Porto will play Russia's CSKA Moscow in the round of last 16 next month.