Sources: 76ers' Ben Simmons (back) to miss undetermined amount of time

Woj: Sixers preparing to be without Simmons for a while (1:05)

Adrian Wojnarowski discusses Ben Simmons' back injury and how long he could be out. (1:05)

PHILADELPHIA -- As the Philadelphia 76ers and Ben Simmons' management team work with doctors to evaluate a course of action on the All-Star guard's injured back, Simmons is expected to be sidelined for an undetermined period of time, league sources told ESPN's Adrian Wojnarowski.

The anticipated length of time missed and next steps in remedying his back injury could be decided as soon as Tuesday.

The injury will have longer-term implications than simply the 76ers' upcoming West Coast trip.

"I don't know," Sixers coach Brett Brown said before Monday night's 129-112 win over the Atlanta Hawks when asked how long Simmons will be sidelined. "It really is kind of, like, how long is a piece of string? Who knows? Who knows?

"Whatever the time equals on days, games, period of time, then we can talk more honestly as this thing shakes out. But as it sits right now, that's how I see the world."

Simmons, who played less than five minutes in Philadelphia's loss to the Bucks on Saturday night before exiting with back soreness, was described by sources as emotional after leaving the X-ray room at Milwaukee's Fiserv Forum.

He also missed Thursday's overtime win at home versus the Brooklyn Nets with lower back tightness.

Simmons, 23, was ruled out of Monday's game. The team said a further determination on a course of action will be decided within 24 hours.

The team declined to put any sort of time frame on how long Simmons would be sidelined.

What is certain, however, is that the Sixers are going to be without Simmons for the immediate future, which includes a trip to Los Angeles to play the Clippers on Sunday and the Lakers on March 3 as part of a weeklong trip through California.

Brown and the Sixers had hoped to spend the opening weeks after the All-Star break solving their yearlong issues on the road. (Philadelphia owns the league's best home record at 27-2, while having one of the worst road marks at 9-20.)

Instead, Brown now must figure how he will survive without his lead ball handler and one of the two pillars of his team, alongside center Joel Embiid.

"It's not ideal," Brown said. "But that's why you have a team. Now, coach it.

"This is the opportunity we have without an NBA All-Star, without a starting point guard, and we will manufacture ball carriers with the group that's been left back outside of Ben not being with us, and what that role looks like and who has that responsibility."

Brown said the Sixers will not try to replace Simmons -- who is averaging 16.9 points, 7.9 rebounds and 8.3 assists this season -- with one player, instead opting for a "point guard by committee" approach. Second-year guard Shake Milton started in place of Simmons on Monday, finishing with 7 points, 5 rebounds and 6 assists. Shooting guard Josh Richardson also played the point.

Meanwhile, the Sixers still have to sort out what else is going on with their team.

Al Horford's role continues to be in flux. After coming off the bench the past three games -- against the Clippers before the All-Star break, and then both Thursday against Brooklyn and Saturday against Milwaukee -- he was reinserted into the starting lineup Monday night and finished with 7 points, 8 rebounds and 5 assists in 31 minutes.

The 6-foot-9 Horford had started 835 straight games since his rookie season in 2007 before Brown took him out of the starting lineup on Feb. 11.

During his pregame media availability Monday, Brown repeated the line he used Friday about Horford's awkward first season with the Sixers after signing as a free agent last summer.

"I have to help him help us," Brown said.

The lack of shooting across the roster remains a problem, as are Philadelphia's ongoing issues away from home. All of that together has left the Sixers, who were expected to be challenging for the top spot in the Eastern Conference with Milwaukee, in fifth place in the conference -- and currently in line to face former Sixer Jimmy Butler and the Miami Heat in the first round of the playoffs.

But as he waits for an update on just how long Simmons will be sidelined, Brown tried to maintain a positive outlook on what the Sixers can learn about themselves with their star guard watching from the sidelines.

"There's 25 games left," Brown said before the 76ers beat the Hawks. "It's an eternity. Just keep going back to the endgame. What's the bottom line? I'll say it again: If you get the health and the spirit, it's got a chance to equal form.

"It's all about landing the plane. That's what the playoffs are. ... We've taken a hit with Ben. I do see it this way. I'm not spinning it. It's an opportunity for us to learn, and something will emerge."

The Associated Press contributed to this report.