Philadelphia 76ers guard Ben Simmons is likely to miss an extended period of time after aggravating a back injury on Saturday, ESPN.com reported Monday.

Simmons missed Monday night’s win over the Atlanta Hawks, and will require further evaluation after leaving in the first quarter of Saturday’s game at the Milwaukee Bucks due to lower back tightness.

What steps Simmons’ management team and doctors will take to improve his physical status could be determined as early as Tuesday. Philadelphia coach Brett Brown sounded unsure of Simmons’ immediate future when asked about his star guard after his team’s 119-112 win.

“I don’t know. It really is kind of, like, how long is a piece of string?” Brown said. “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.”

Hurt while going up for a rebound in practice on Wednesday, Simmons aggravated his back injury midway into the first quarter of Saturday’s 119-98 loss to the Bucks, playing less than five minutes. He was “emotional” after leaving the X-ray room in the Bucks’ arena.

Simmons winced in pain after going up for a layup. He exited the contest and immediately retreated to the locker room.

The 23-year-old recorded 17 points and six rebounds in the All-Star Game before sitting out the 76ers’ 112-104 overtime victory against the visiting Nets on Thursday with a balky back.

Simmons, who was the top overall pick of the 2016 NBA Draft, is averaging 16.9 points, 8.2 assists, 7.8 rebounds and a league-leading 2.1 steals this season.