However, they square off against opposition in Belenenses who join them in possessing the best defensive record in the division.
After their shock defeat to LASK Linz in the Europa League qualifying rounds, few would have expected Sporting to put together a 12-match unbeaten streak in all competitions.
The league leaders were far from their best during their last-gasp win over Farense, but the result has kept the pressure on the chasing pack heading into 2021.
With Porto and Benfica having contested the Super Cup earlier this week, Ruben Amorim's team have the opportunity to move five points clear ahead of the two biggest clubs in Portugal.
The pressure remains off Sporting to a certain degree with few people expecting anything better than third place, but a ninth league win in 11 will only increase expectations at Estadio Jose Alvalade.
Pedro Goncalves, formerly of Wolverhampton Wanderers, has been a revelation since arriving from Famalicao, but the playmaker's six-match scoring streak came to an end in Sporting's last fixture.
Goncalves has scored twice as many strikes as the entire Belenenses squad, a remarkable statistic which only suggests that the home side could struggle on Sunday evening.
Nevertheless, Nuno Oliveira's team have matched Sporting for only conceding seven times in 10 matches, two of which came in the same game at Benfica.
Oliveira will naturally want to see more productivity in the final third, but the Belenenses boss is unlikely to tinker with his tactics for a game of this magnitude.
Os Azuis do Restelo are also coming off the back of a defeat to Maritimo, a setback which has left the club within reach of every team below them in the table.
Belenenses Primeira Liga form: LDDDWL
Belenenses form (all competitions): DWDWLW
Sporting Lisbon Primeira Liga form: WWWWDW
Sporting Lisbon form (all competitions): WWDWWW
Andraz Sporar is pushing for a recall to the Sporting XI after netting in his last two appearances in all competitions.
Belenenses possible starting lineup:
Oliveira; Henriques, Henrique, Ribeiro; Esgaio, Sithole, Ramires, Lima; Varela, Cardoso, Sousa
Sporting Lisbon possible starting lineup:
Adan; Neto, Coates, Feddal; Porro, Palhinha, Mario, Mendes; Goncalves, Tabata; Sporar
We say: Belenenses 1-2 Sporting Lisbon
Despite the home side losing their way in recent weeks, we still expect them to provide Sporting with one of their toughest tests of the season. However, the leaders are motivated to remain undefeated heading into 2021, and the visitors could edge a tight game on Sunday evening.