Gregorius will hit third and play second base for Triple-A Tacoma on Friday, Paul Braverman of the Tacoma Rainiers reports.
Gregorius signed a minor-league contract with the Mariners on Thursday, Russell Dorsey of Bally Sports reports.
Gregorius signed a contract Monday with Algodoneros de Union Laguna of the Mexican League.
The Phillies released Gregorius on Thursday.
Gregorius isn't starting Friday against the Pirates.
Gregorius is out of the lineup for Monday's game in Atlanta.
Gregorius went 2-for-4 with a two-run home run and two additional RBI in Saturday's 10-0 rout of the Phillies.
Gregorius went 0-for-2 with a walk and a stolen base in Friday's 2-1 win over the Marlins.
Gregorius is out of the lineup for Sunday's game against the Cardinals.