The Giants elected to go with Fabiano and sign him to their practice squad over Gradkowski.
Gradkowski has worked four the Colts and Patriots since he became available.
Gradkowski, 28, is a former fourth-round pick of the Ravens back in 2012. The Panthers signed Gradkowski to a three-year, $3.15 million contract last year and he set to make a base salary of $875,000 for the 2017 season.
The Panthers placed Gradkowski on injured reserve back in September and later released him with an injury settlement.
In 2016, Gradkowski appeared in 10 games for the Panthers and is rated by Pro Football Focus as the No. 33 center out of 37 qualifying players.