Porto and Benfica both missed a chance to kick clear of each other at the top of the Liga Sagres table after being held to draws on Sunday.
Porto were forced to come from behind to earn a point in a 1-1 home draw against lowly Olhanense.
Olhanense, who entered the game without a victory in five matches, started brightly and claimed a shock lead after just seven minutes through Targino.
It was one of just three shots on goal Olhanense would have for the game - in stark contrast to Porto's 29 - but they defended for their lives and frustrated the home crowd.
They managed to carry their lead into half-time before Colombian Jackson Martinez finally levelled on 55 minutes.
No further goals were in store though as Porto were left frustrated by the valiant, defiant showing from their opponents.
In a match that saw three red cards dished out, Benfica played out an entertaining 2-2 draw at Nacional.
Nacional took the lead thanks to Diego Barcellos' early goal after six minutes but a Mexer own goal and a strike from Uruguayan Jonathan Urretaviscaya put Benfica in front at the break. Mateus equalised eight minutes into the second half before a fiery ending to the game saw referee Pedro Proenca kept busy.
Benfica pair Nemanja Matic and Oscar Cardozo were both given straight reds, as was Brazilian defender Fernando Marcal for their opponents.
Nacional players Barcellos and Gottardi also received yellow cards in the heated end to the match.
Both Porto and Benfica are locked level on 46 points from 18 matches, with the third-placed Pacos de Ferreira already 15 points behind them.
Other results on Sunday saw the fifth-placed Rio Ave defeat Academica 2-1 thanks to goals from Ahmed Hassan Koka and Bebe.
South Korean Hyun-Jun Suk bagged the game's only goal as Maritimo won 1-0 at Sporting Lisbon and Vitoria Setubal beat Gil Vicente by the same scoreline.
Moreirense also won, cruising to a 3-0 win over Beira-Mar with Nabil Ghilas scoring a double for the winners.