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.
Hernandez, however, wasn't overly concerned at his pitching line.
''We're in spring training, man,'' he said. ''I don't look at any results.''
The 2010 American League Cy Young Award winner might have also had a bit of bad luck in the form of a couple of well-placed hits - a slow-rolling infield single and a flyball that dropped just in front of diving right fielder Corey Hart - as he worked through the Rangers' lineup.
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.
In between starts, Hernandez said he paid special attention to working on his changeup. He liked the results he saw Sunday.
''Changeup was good, much better,'' he said. ''Feel was better. I think the mechanics were way better.''
Seattle's reserves scored six runs in the eighth, erasing Texas' five-run lead.
Rangers: Colby Lewis, also making his second spring appearance, held the Mariners scoreless over two innings, allowing a hit, a walk and struck out one. Texas manager Ron Washington was pleased with Lewis' outing.
''He was able to command his fastball, he had a good slider working, changeup,'' he said. ''It was a nice outing for Colby.''
Lewis signed a minor league contract in November with Texas after missing last season because of injuries.
''We're just going to keep ramping him up and see how he withstands it,'' Washington said. ''So far, so good.''
Rangers: Right fielder Alex Rios is nursing a mild right intercostal strain and did not play in a game for the fifth day in a row. Washington said Rios has been doing everything in practice except swing a bat and might return in the next two days.
''Just don't want to take a chance swinging right now because he could aggravate it,'' he said. ''We're going to let it settle down before we put him back out there. But he's doing infield and throwing and running balls down in the outfield. Just not swinging the bat.''
Outfielder Engle Beltre returned to action after sitting out the previous six days because of shin splints.
Mariners: Second baseman Robinson Cano has not played since having root canal surgery on Wednesday. Seattle manager Lloyd McClendon said there was a good possibility Cano would play Monday against Kansas City.
New Seattle closer Fernando Rodney struggled in his second spring training appearance. Rodney, who signed a two-year, $14-million contract in February, gave up a two-run single to Robinson Chirinos in the fifth. In two-third of an inning, Rodney allowed two earned runs on two hits and a walk, while striking out one.
Choice, Texas' cleanup hitter, hit his first homer of spring training, a solo shot off Zach Miner in the sixth inning. The right fielder went 1-for-3 with three runs scored.
''He's been doing a great job, he really has,'' Washington said of Choice, the backup at all three outfield positions. ''Playing good defense, swinging the bat and he caught one today.''
Rangers: Ace Yu Darvish was scheduled to make his third start of spring training Monday against Cincinnati right-hander Homer Bailey. Also scheduled to pitch for Texas were Joakim Soria, Ryan Feierabend, Neftali Feliz and Aaron Poreda.