Making his second Cactus League start, Hernandez (1-1) allowed four hits and walked one, while striking out four. Hernandez opened the game by issuing a leadoff walk to Jurickson Profar before sandwiching a pair of strikeouts around a flyout by Prince Fielder.
Fielder got the best of Hernandez in the third, though, when he lined a double that scored Elvis Andrus and sparked a four-run inning. Hernandez left the game one batter later after striking out Michael Choice, who reached on a wild pitch.
Texas starter Colby Lewis, also making his second spring appearance, held the Mariners scoreless over two innings.
Seattle's reserves scored six runs in the eighth, erasing Texas' five-run lead.
The Mariners return to action Monday with a split squad game against Kansas City in the afternoon, and then they follow that up with a night game against Arizona.