Porto moved level on points with leaders Benfica after a 3-0 win over lowly Vitoria Setubal on Wednesday in the Liga Sagres.
Jackson Martinez took his season tally to a league-best 14 goals with a brace, while Luis Gonzalez added a third in stoppage time.
Struggling Setubal fell behind to Martinez's penalty on nine minutes and were dealt a blow when Bruno Gallo received a red card for a second bookable offence in the 78th minute, just three minutes after coming on.
Striker Jorginho Sousa made matters worse when he was dismissed for a second yellow on 85 minutes.
Martinez bagged his second a minute later and Porto eased nerves as they made the most of the two-man advantage to make it 3-0 with Gonzalez's goal in the 91st minute.
Porto trail Benfica on goal difference with both on 39 points after 15 games.