Benfica’s six match winning run came to an abrupt end at Rio Ave despite taking a third minute lead when Salvio converted a superb diagonal through ball from Pizzi.
Rio Ave then lost top scorer Hassan and defensive cornerstone Marcelo, both injured before half-time.
It was certainly a game of two halves as Rio Ave came out fired up for the second period and Benfica looked as if they only had to go through the motions to win.
But all that was to change when Samaris handled in the box and Rio Ave substitute Ukra stepped up to level the score with fifteen minutes remaining.
Ten minutes later Benfica captain Luisão was sent-off for bringing down Tiago Pinto and in a thrilling climax Del Valle slotted home from a tight angle to silence the large contingent of travelling fans.
FC Porto kicked off shortly after the Benfica game had finished, knowing that a win against Nacional would propel them to within one point of the leaders.
The visitors appeared to have one eye on their upcoming Champions League quarter-final against Bayern Munich as they struggled to create any rhythm in their play. Even so Cristian Tello came up with a super individual effort just before the break, finding the top corner of the net from the edge of the box.
Nacional proved much more dangerous after the break and duly got their equaliser through substitute Wagner. Minutes later and they should have taken the lead but Luca João produced one of the misses of the season as he ballooned an inviting cross over the bar from just six metres.
The 1-1 draw leaves a three point gap at the top and the championship could be decided in late April when Benfica and FC Porto clash at the Stadium of Light.
Sporting Lisbon are six points behind Porto after an impressive win over Vitória Guimarães.
João Mário put the home-side in front when he headed home a cross by Carrillo. Adrien added a second from the penalty spot and Slimani made it 3-0 on the stroke of half-time.
A second penalty, this time converted by Nani, extended Sporting’s lead before Kanu scored a consolation for Vitória. Third-placed Sporting are now nine points clear of Braga in fourth who were held to a 0-0 draw at home to Académica.
In the Second Division SC Portimonense drew 1-1 at home to Algarve rivals SC Olhanense. The home side were awarded a contentious penalty for handball midway through the second-half which Ricardo Pessoa duly converted.
Olhanense levelled matters ten minutes later when Diakhité headed home from a corner.
This was the visitors sixth game undefeated as they struggle to pull away from the relegation zone. On Easter Saturday (4 April) Olhanense entertain Benfica ‘B’ in Olhão kick-off 8.30pm. SC Farense, despite playing with ten men for the whole of the second-half, battled to a 2-1 victory over promotion hopefuls Freamunde.
Okechukwu Irobiso scored after just four minutes before Bruno Gonzalez picked up two yellow cards in the space of three minutes just before the interval. Yang Tan added a second ten minutes after the break with Freamunde reducing the arrears deep into stoppage time through Djim.