Wentz had been listed as doubtful on the Eagles' injury report after not practicing all week.
Head coach Doug Pederson told reporters on Friday that Wentz has been dealing with a stress fracture in his back that has gotten worse as time has passed.
"He has a stress injury, evolved over time and it requires no surgery," Pederson said. "[I'm not] answering any more questions about it. We're playing the Rams in two days, if you guys haven't figured this out."
NFL Network's Ian Rapoport reported on Wednesday the Eagles made no determination about putting Wentz on injured reserve, but "they won't put him at risk" to do more damage to his back.
Wentz has had a strong 2018 season, completing a career-high 69.6 percent of his passes with 3,074 yards, 21 touchdowns and seven interceptions in 11 games since returning from a torn ACL he suffered last season.
The Eagles (6-7) face an uphill climb to get back to the playoffs with Nick Foles at quarterback. They are one loss behind the Minnesota Vikings for the final wild-card spot in the NFC with three games remaining.