ESPN's Adrian Wojnarowski added, "There's no timeline for a Simmons return, but an evaluation in two weeks is more of an initial benchmark date than an expectation of a quick return to the lineup."
Simmons initially tweaked his back in the Sixers' first practice after the All-Star break. He missed the team's 112-104 win over the Brooklyn Nets on Thursday but returned to the floor during Saturday's loss to the Milwaukee Bucks.
However, Simmons was forced to leave the loss early after aggravating the back injury.
According to Charania, Simmons "will undergo daily treatment and rehab after he consulted with several specialists internally and externally."
A two-time All-Star, Simmons has been superb for the Sixers this season as they seek to find some footing in a crowded Eastern Conference.
To date, he's averaged 16.7 points, 8.2 assists, 7.8 rebounds and a league-leading 2.1 steals per game while shooting 58.5 percent from the field.
Shake Milton should handle more extensive duties at point guard for the time being, while the newly acquired Alec Burks figures to slot in as a secondary on-ball playmaker.