Milwaukee Bucks star Khris Middleton is expected to miss Wednesday's season opener against the Philadelphia 76ers, sources told ESPN on Monday.

The three-time All-Star will be out to start the NBA season as he rehabs from offseason ankle surgeries, and the Bucks are cautiously progressing Middleton toward a return, sources told ESPN.

Middleton did not appear in a preseason game and still hasn't been cleared to participate in the team's 5-on-5 scrimmages at practice. He had participating in 3-on-3 scrimmages for most of the preseason, but Bucks coach Doc Rivers told reporters over the weekend that Middleton has been limited in practice since Wednesday.

Taurean Prince has been filling in in the starting lineup during the preseason during Middleton's absence.

Middleton sprained his left ankle in a Feb. 6 game against the Phoenix Suns after he landed on Kevin Durant's foot following a jump shot. Middleton then missed the next 16 games with the injury, which he called the worst ankle sprain of his career; it lingered all season.

Middleton, who averaged 15.1 points, 4.7 points and 5.3 assists during the regular season, underwent surgery on it shortly after Milwaukee's season ended in May.

The right ankle injury occurred during Game 2 of the Bucks' first-round playoff loss to the Indiana Pacers. The injury kept him from practicing during the playoffs, but he played through it to average 24.7 points, 9.2 rebounds and 4.7 assists in helping Milwaukee fight in the series without an injured Giannis Antetokounmpo. He had surgery on it in June.

Middleton, 34, has only appeared in 88 regular-season games across the past two seasons because of a number of lingering injuries. In April 2022, he sprained his knee during the Bucks' first-round playoff series and then had wrist surgery during the 2022 offseason.

In the summer of 2023, he had right knee surgery and was kept on a strict minutes restriction for most of the first half of the season.

ESPN's Jamal Collier contributed to this report.