Benfica will be without Alexander Bah and Manu Silva for next week's Champions League play-off against Monaco after the club announcing on Sunday that both had torn knee ligaments.
Both players were replaced in the first half of Saturday's game against Moreirense, defender Bah going off after 34 minutes and midfielder Silva hobbling off three minutes later.
In a press release, Benfica announced that Bah and Silva both had a "sprained left knee with complete rupture of the anterior cruciate ligament".
Striker Angel Di Maria, who missed Saturday's game because of a muscle injury, is also a doubtful starter against Monaco.
Benfica, who play their play-off first leg in Monaco on Wednesday, beat Moreirense 3-2 with Vangelis Pavlidis scoring two penalties and Nicolas Otamendi adding the third.
They remain second in the league four points behind leaders Sporting Lisbon.