Greenlaw (quadriceps) didn't practice Wednesday, Vic Tafur of The Athletic reports.
Greenlaw injured his quad during the fourth quarter of the 49ers' 36-30 win over the Cardinals in Week 3, when he logged eight tackles (three solo). The veteran linebacker will need to return to practice in at least a limited capacity over the coming days to have a realistic chance of playing against the Broncos on Sunday. If Greenlaw is unable to play, then Garret Wallow would likely start alongside Fred Warner and Jaden Dugger at linebacker.