The Philadelphia 76ers will miss their superstar center Joel Embiid in the coming Game 1 of the NBA Eastern Conference semifinals against the Boston Celtics, according to their head coach Doc Rivers.

"There is no latest. Obviously, the doctors looked at him (Embiid), and he didn't do anything today," Rivers said on Saturday. "I'll say this, but if I was a betting man, I would probably say doubtful for at least Game 1. But we'll see."

Embiid suffered a sprained lateral collateral ligament (LCL) in his right knee in Game 3 of the first-round playoffs against the Brooklyn Nets. He sat out the following Game 4 while his side swept the opponents 4-0. Though the Celtics played more games than expected to eliminate the Atlanta Hawks, giving Embiid more time to recover. It seems unlikely he will get back in time.

If Embiid misses Game 1, the 76ers are likely to start Paul Reed instead of Montrezl Harrell in the center position. Reed has averaged 7.4 points and seven rebounds in 16.3 minutes per game against the Hawks.

"I keep the same mental preparation and physical preparation as I would even if he was playing," Reed said. "I won't change up what I'm doing any differently. I keep the same mental focus."

Reed doesn't shoot 3-pointers at all. Neither is he a dominant isolation scorer like Embiid. Therefore, the Celtics have good reasons to add Robert Williams III to the starting lineup. He played as the backup center in all of the six games against the Hawks because the team needed Al Horford's 3-point shooting ability to break the opponents' drop-back defensive policy.

Nonetheless, Williams averaged 1.3 blocks in 22.8 minutes per game in that series while keeping an 88.5-percent field goal rate. He and Reed are both 2.06 meters tall, but Williams III is 12 kilograms heavier and much more athletic. Reed is unlikely to bully Williams III in the low post or keep him from finishing next to the hoop. As an agile center, Reed will probably close out and switch defensively, making it less valuable to make Horford play center to keep a five-out squad on the court.

Williams III's style of playing can also help the Celtics contain James Harden. Without Embiid, the 76ers will count more on Harden to score. Having aged and gone through a series of injuries, Harden is much less explosive today. He shot poorly within the 3-point line in the series against the Nets. With the Celtics' defensive resources, they have a good chance of freezing Harden at the TD Garden in Boston, Massachusetts, on May 1.