Bucks' Giannis Antetokounmpo, Damian Lillard out for Game 4 - ESPN

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

Lillard aggravated an Achilles tendon injury late in the fourth quarter of Friday's 121-118 overtime loss to the Pacers, which gave Indiana a 2-1 lead in the series.

A source told ESPN the injury is a strained right Achilles tendon, as first reported by The Athletic. An eight-time All-Star, Lillard was seen with a walking boot on his right foot Saturday.

Lillard's Achilles has been bothering him for a few weeks. He revealed he had been feeling some discomfort following Milwaukee's regular-season finale in Orlando and then sat out the first few days of practice before the start of the playoffs to recover, a break 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.

A two-time NBA MVP, Antetokounmpo hasn't played since straining his left calf in a game on April 9.

The series returns to Milwaukee for Game 5 on Tuesday.

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