Harrison (hamstring) was placed on the Active/PUP list Friday, Michael Eisen of Giants.com reports.
Harrison hasn't played in an NFL game since 2019, but he signed a one-year, $2 million contract to serve as the Giants' backup center for the 2021 season. It is unclear how severe the 29-year-old's hamstring injury is. Once he gets healthy, the Florida product is be eligible to return from the PUP list at any time during training camp.