General manager John Lynch said that McKinnon (knee) suffered a setback in Tuesday's practice, Eric Branch of the San Francisco Chronicle reports.
Lynch also noted that McKinnon's return to practice Tuesday was "not encouraging." Coach Kyle Shanahan previously indicated that McKinnon had a chance to suit up for the Week 1 matchup with the Buccaneers, but the running back's availability for the season opener is now trending in the wrong direction. McKinnon has had a bumpy recovery while working his way back from a right ACL tear that sidelined him for the entire 2018 season and looks to be behind both Tevin Coleman and Matt Breida in the backfield pecking order.