Shepard injured his ankle at Wednesday's practice and was taken off the field on a cart.
Initial tests revealed a "rolled, basketball ankle," according to Giants head coach Ben McAdoo. The MRI is precautionary.
"To make sure we're looking at it and doing our due diligence," McAdoo explained.
The Giants were optimistic Wednesday evening that the injury isn't anything serious, but they were waiting for the swelling to subside before coming to a final verdict, sources told ESPN. Shepard's left foot is expected to be in a boot. He was not outside while the Giants practiced Thursday.
Shepard, 23, made 65 receptions for 683 yards and eight touchdowns last season. He was second among all rookie wide receivers in touchdowns.
The Giants have high hopes for their receiver corps this season with Shepard working alongside Odell Beckham Jr. and Brandon Marshall. Shepard is the Giants' starting slot receiver. He played more snaps (804) in the slot last season than any player in the NFL. San Francisco's Jeremy Kerley was second with 700 snaps out of the slot.
Tavarres King stepped in to take most of the first-team snaps with Shepard sidelined at Thursday's practice. But King left early with an ankle injury suffered during a special-teams drill.
Other injury updates:
Linebacker Keenan Robinson (concussion), offensive lineman Jessamen Dunker (foot) and cornerback Valentino Blake (back) also missed practice. Linebacker B.J. Goodson left practice early and had his foot taped. His injury is not expected to be serious.