Hernandez was added to the Mariners' major-league roster Saturday.
Hernandez was claimed off waivers by Seattle on Friday after he was designated for assignment by the Rangers earlier in the week. He will now join Seattle's bullpen ahead of the second game of their series at home against the Phillies. Hernandez has produced a 5.05 ERA and 1.59 WHIP with 36 strikeouts over 41 innings in 26 appearances with the Rangers this season.