CAMDEN, N.J. -- Philadelphia 76ers coach Doc Rivers said Saturday afternoon that if he "was a betting man," superstar center Joel Embiid will be doubtful to play in "at least" Monday's Game 1 of the titanic Eastern Conference semifinal against the Boston Celtics.

"There is no latest," Rivers said, following Philadelphia's practice at the team's facility. "Obviously, the doctors looked at him, and he didn't do anything today.

"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."

When asked what it will take to get Embiid, who is dealing with a sprained LCL in his right knee suffered in Game 3 of Philadelphia's first-round sweep of the Brooklyn Nets, back on the court, Rivers had a simple response.

"He has to get better," Rivers said with a wry laugh.

Rivers added that Embiid was able to do nothing in practice.

"Nothing yet," he said. "Just wasn't able to. And, obviously, we were hopeful for today."

Embiid's injury happened nine days ago, and when the media was let into practice Saturday afternoon, he -- along with P.J. Tucker and others -- was not on the court. Embiid sat out Game 4 against the Nets last week, meaning he will have an 11-day break between the last time he played and Game 1 of the East semifinals Monday night at Boston's TD Garden.

The update from Rivers, though, casts a pall over that game from Philadelphia's perspective. If the leading candidate to be named the NBA's Most Valuable Player is unable to play in Game 1, the 76ers will then shift their focus to him potentially returning Wednesday in Game 2.

In the meantime, the 76ers are preparing for multiple contingencies. If Embiid is unable to go in Game 1, reserve Paul Reed would likely step into the lineup in Embiid's place.

"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, an energetic, bouncy big, was impressive filling in for Embiid in Philadelphia's closeout win over the Nets in Brooklyn this past Saturday, putting up 10 points, 15 rebounds, 2 assists, a steal and a block in 32 minutes.

The third-year big man out of DePaul said that performance gave him confidence that, if Embiid is unable to play in Game 1, he'll be able to step in and produce for the 76ers once again.

"It does a lot for my confidence knowing I can step in and play valuable minutes for the team and give us a boost that we needed in order to close out that series," Reed said. "So now I feel I can go into the next series and give us another boost. If Joel is not playing, I'm confident I can come in and give us a lot of energy and help us win."

Whether Embiid is available or not, the 76ers still have to prepare to take on their blood rivals in the Celtics, a team they will be facing in the postseason for a 22nd time in the long and illustrious history of the franchises.

Rivers and Reed said playing the Celtics was the expectation all along, even as Boston gave the Sixers a couple extra days for them to prepare and Embiid to rest by blowing a big fourth-quarter lead in Game 5 against the Atlanta Hawks.

Rivers, who led Boston to its last championship 15 years ago, praised the Celtics for their depth and playoff experience, which he said will help them navigate the weeks ahead.

"A lot of things," Rivers said. "They're a terrific team, they're well-coached, they spread the floor, they attack, they're deep, they have a lot of weapons.

"Obviously Tatum and Brown, but Horford, White, Brogdon, you just keep going down the list. They just have a lot of guys that can play basketball, and like I've said with other teams, they're made. They've been to the Finals. They get it. They've been through any type of adversity. Nothing is going to shake them. And you've got to be ready for that."