Garoppolo (calf) didn't return after halftime in Sunday's loss to the Seahawks and will get an MRI on the injury Monday, David Lombardi of The Athletic reports.
Garoppolo actually suffered the injury on the opening drive but was able to stay in the game until halftime. Rookie third-overall pick Trey Lance took over under center at halftime and would start against the Cardinals in Week 5 if Garoppolo can't go, though the starting job will remain in Garoppolo's hands if the MRI result reveals no significant damage and he's able to suit up in Arizona. Per Doug Kyed of Pro Football Focus, Garoppolo anticipates that the injury will sideline him for a couple weeks.