The team announced the injury after the Giants' first day of camp concluded. Shepard underwent post-practice X-rays, which revealed his left thumb injury.
Shepard sustained the injury while attempting to catch a low pass. The team said he will be evaluated on a week-to-week basis.
The fourth-year wideout started all 16 regular-season games and finished with career highs in receptions (66) and yards (872) last season. He signed a contract extension with the Giants in the off-season.
After the departure of star receiver Odell Beckham Jr. to the Cleveland Browns in an off-season trade this year, Shepard is expected to fill in as the team's top pass-catcher. Giants head coach Pat Shurmur said he believes the Oklahoma product can be a No. 1 receiver.
"Sure, I think he can be," Shurmur said. "Sterling is a football player, and we appreciate his toughness and his ability to make plays, and all the things he adds to the team. He's a value-added guy in my mind. He plays his position, but he makes the people around him better. I think that's what all the players should strive to do."
The Giants selected Shepard in the second round of the 2016 NFL Draft out of Oklahoma. He was named to the PFWA All-Rookie Team in 2016. In 43 career games, he has recorded 190 catches for 2,286 yards and 14 touchdowns.