The champions a suffered a surprise 2-1 defeat at 10-man Boavista on Saturday, but with their two nearest challengers failing to find a winner at the Stadium of Light, their position remains strong.

Liedson silenced the hostile home crowd with a first-minute opener for Sporting only for in-form Italian Fabrizio Miccoli to equalise in the 23rd minute.

Both sides pushed for a winner in the second half but the game finished even, leaving Porto three points clear of Sporting and four from third-placed Benfica.

Mid-table Nacional managed a 1-0 win at home to Estrela Amadora, with all the action saved until the final few minutes.

Juliano Spadacio scored Nacional's winner in added time, while Luis Loureiro was given a head-start to the shower cubicles by referee Nuno Miguel Serrano Almeida.

Aves secured three priceless points in their battle to beat the drop with a 1-0 win at Naval.

Jorge Ribeiro's strike shortly before the hour mark took them above Setubal to third from bottom, three points from Academica in 13th and safety.

Setubal's 1-1 draw at home to Maritimo would have represented a decent result had Aves not won on Sunday.

Marcelo Lipatin had given Maritimo the advantage seven minutes into the second half on the coast, but Silvestre Varela forced a 66th-minute leveller to take an important point.

Beira Mar remain rock-bottom following the 2-0 defeat by Belenenses on Saturday.