Gray is expected to join the club on Saturday, when the Mariners will have to make another move to get him on their roster. The 29-year-old had a 2.70 ERA in six appearances for the White Sox this season. Four of his outings were scoreless, and he threw three shutout innings on May 10 against the Angels.
Gray has also pitched with Oakland and the Cubs. He's 1-1 with a 4.36 ERA in 42 games.