Sporting Lisbon were surprisingly beaten by Victoria Guimaraes in their last league game and that has affected their position on the league table.
They are currently 5 points below league leaders, FC Porto and 1 behind second placed Benfica, so only a win for them in this game would be enough for them to keep the pace.
Apart from their shock 1-0 loss at Viktoria they have won 6 of their last 7 league games. Scoring goals has also not been a problem as they have at least 3 goals in 6 of their last 7 games in all competition.
Belenenses are also not having a particularly bad season at the moment. They are currently 6th in the Portuguese top flight table ahead of this game.
They have lost twice to FC Porto in their last six games, but they come into this game having not lost any of their last 8 league games.
They have the chance to move above Viktoria if they can win this game by two or more goals ahead of the pair facing each other on Sunday. That could be added incentive for the visitors to go all out for the win.