Bucks players Giannis Antetokounmpo and Damian Lillard will be absent from the fourth game

Milwaukee Bucks stars Giannis Antetokounmpo and Damian Lillard have been ruled out of Game 4 of their first-round Eastern Conference series against the Indiana Pacers on Sunday in Indianapolis.

Lillard aggravated an Achilles injury late in the fourth quarter of a 121-118 overtime loss to the Pacers on Friday, giving Indiana a 2-1 lead in the series.

A source told ESPN that the injury was caused by a strain in his right Achilles tendon, as first reported by The Athletic. Lillard, an eight-time All-Star, was seen wearing a walking boot on his right foot on Saturday.

Lillard's Achilles tendon has been bothering him for a few weeks. He revealed that he was feeling some discomfort after Milwaukee's regular-season finale in Orlando and then missed the first few days of practice before the start of the playoffs to recover, a break that Lillard said helped him feel fresh entering the series.

Lillard, 33, is averaging 32.3 points, 5.3 assists, 3.7 rebounds and 1.3 steals in three games in the series.

Antetokounmpo, the two-time NBA MVP, has not played since injuring his left calf in an April 9 game.

The series returns to Milwaukee for Game 5 on Tuesday.

ESPN's Jamal Collier and Field Media contributed to this report.