The AL West-leading Rangers pounded Hernandez for nine runs and 11 hits in three-plus innings on Wednesday en route to a 12-4 win over the Mariners.
Hernandez fell to 0-4 with a 7.57 ERA in five starts against the Rangers this year. The right-hander's 20-career losses against Texas are his most against any team.
"We don't own him. No one owns him," Rangers manager Ron Washington said. "He's only human and there's some days he's going to go out there and things aren't going to fall into place. Fortunate for us, today was one of those days."
Hernandez struggled early on Wednesday.
Leonys Martin started the scoring with two outs in the second, slicing a 2-1 pitch into the Seattle bullpen in left field. The three-run home run was part of a career-high four RBIs game for Martin.
Texas kept the pressure on with two more runs in the third and five in the fourth. Ian Kinsler chased Hernandez (12-8) in the fourth with a run-scoring single, the fourth straight hit for the Rangers to open the inning.
"Felix is always a great challenge to face," said Elvis Andrus, who had three of the team's 17 hits.
"Every time you face one of the best pitchers in the league, it's a great challenge to be able to beat him. We know we have to do every little thing. Don't try to make him feel comfortable on the mound and that's what we did today."
"I thought he was up for the most part and they were ready to hit," Mariners manager Eric Wedge said. "They are a good hitting ballclub, ready to hit it."
While the offense gave him an early lead, Martin Perez (8-3) limited the Mariners to two runs and five hits in six innings. Perez breezed through the Mariners lineup, not allowing a hit until Kyle Seager's one-out single in the fourth.
The right-hander won his fifth straight decision -- he hasn't lost since July 21 -- and is the first Texas rookie pitcher to win five consecutive starts.
"He's growing," Washington said. "You're watching it right in front of your eyes. I just think you need to watch it and enjoy it. He just goes out there and does what he does. That's throw the fastball down in the zone, change speeds and use his breaking ball and move it around."
The three innings pitched for Hernandez ties the second-shortest outing of his career. The former AL Cy Young winner's ERA climbed from 2.63 to 2.97.
Dustin Ackley hit a solo home run and an RBI double for the Mariners, who have lost six straight games. Seager hit his career-high 21st homer in the sixth, a drive to right that struck a window in the second deck.
The Mariners said they will select top pitching prospect Taijuan Walker from Triple-A Tacoma and the 21-year-old right-hander will make his major league debut on Friday. ... Ackley is hitting .356 since the All-Star break to raise his season average to .253. He has two home runs in his past four games, after hitting just one in his first 85. ... Perez leads AL rookies with eight wins.