Branyan drove a 1-0 pitch from Bobby Seay (1-2) into the stands in right-center for his 24th homer -- the last of Seattle's two hits in the game.
"Slider, caught the middle. That's about it," said Branyan, who matched his career high in home runs.
Hernandez (11-3) struck out eight in seven innings, allowing one run and six hits. He overcame a slow start and twisting his ankle in the third.
"He battled his pitch count," Mariners manager Don Wakamatsu said. "He battled and survived to go seven and we could stack up our bullpen with Aardsma and Lowe."
"They were jumping on the fastball," Hernandez said.
"He's tough, because he's got such a good, hard slider," Anderson said. "He threw me a pitch, the gun said 93 with his slider. I don't know if he's got a 90 mph slider, but he did tonight. He threw me a slider, a hard one."
Hernandez twisted his ankle in third when he tried to catch Thames' blooper between himself and second basenman Jose Lopez. He fell and was unable to make the play and Thames was credited with a single.
Wakamatsu and trainer Rick Griffin came out and Hernandez stretched and tested the ankle, finally taking a couple of warmup pitches. He only allowed one hit in 4 1/3 innings after that.
And when Branyan hit his home run, Hernandez was jumping for joy in the dugout.
"Rick [Griffin] was like, 'You're jumping around. You feel good, huh?'" Hernandez said with a smile after the game.
Armando Galarraga matched Hernandez with a terrific outing for the Tigers, yielding one run and one hit in 7 1/3 innings.
"I felt good, really good. Sliders, two-seamers, and my location's getting better," Galarraga said. "I'm doing good things."
Ichiro Suzuki grounded into a shortstop-to-third fielder's choice before Branyan connected.
Thomas gave the Tigers a 1-0 lead with a two-out RBI single in the third.
Hernandez got his 50th career win. ... Detroit 3B Brandon Inge didn't start because of patella tendinitis in both knees. He entered in the field in the eighth and struck out swinging to end the game. ... Wakamatsu said CF Franklin Guiterrez, who bruised his left elbow and left knee attempting to make a leaping catch against the right-center field wall on Tuesday night, could play on Thursday. Gutierrez's biggest obstacle is a stiff neck. ... Tigers OF Carlos Guillen, on the disabled list with right shoulder inflammation, played at Triple-A Toledo on a rehab assignment on Wednesday night. ... Wakamatsu said LHP Ryan Rowland-Smith, who is at Triple-A Tacoma, will be called up to start Friday's home game against Cleveland. ... Thomas batted cleanup for the first time in his career. ... Detroit slugger Miguel Cabrera's two-out double in the fifth extended his hitting streak to a career-high 17 games.