Bucks' Giannis Antetokounmpo, Damian Lillard miss Game 4

Damian Lillard leaves the game with apparent leg injury (0:59)

Damian Lillard exits the game in the first quarter after suffering an apparent leg injury. (0:59)

Milwaukee Bucks stars Giannis Antetokounmpo and Damian Lillard were 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 didn't participate in shootaround Sunday. Bucks coach Doc Rivers said Sunday that an MRI revealed "just Achilles stuff" for Lillard and that they're not shutting him down.

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. He worked out on Sunday, and it went well, Rivers said.

"He moved. He shot. He's running with no resistance. Those are all very good signs," he said.

Rivers said he was still feeling optimistic about Giannis' status going forward in the series.

"I think there's a chance for him to play in this series, I really do," he said.

The series returns to Milwaukee for Game 5 on Tuesday.

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