"I thought he looked great," Mariners manager Eric Wedge said. "He was efficient, he was strong, he used all his pitches and had great command. He looked fantastic tonight."
San Diego pitcher Tyson Ross, trying to win a job in the starting rotation, allowed one run on four hits in 4 2/3 innings. He walked two and struck out six, throwing 94 pitches.
"His stuff was great, velocity was there, good slider and he even mixed in a couple of changeups," Padres manager Bud Black said. "But overall, he was a little spotty on the ball-strike ratio. But we saw some strides."
Minor Leaguer Christopher Taylor had a two-run single in the eighth inning to give the Mariners the lead.
Seattle's Kelly Shoppach hit a home run, his first of the spring, in the fifth inning for a 1-0 lead.
The Padres got both of their hits off Hernandez with two outs in the second inning, as Nick Hundley had a single and moved to third base on a double by Cameron Maybin. But Hernandez got Alexi Amarista to ground out to end the inning.
After striking out twice against Hernandez, Yonder Alonso hit a home run in the seventh inning, his fourth of the spring. The home run came off Seattle reliever Danny Farquhar.
Seattle third baseman Kyle Seager, who entered the game hitting .238, had two hits, including a double in the seventh inning. Dustin Ackley added two hits as well.
Up next: Time is running out for Padres pitcher Freddy Garcia to make a good impression. Garcia gets the start in a 7:05 p.m. PT game against the Rockies on Saturday at Salt River Fields. Garcia, who is scheduled to go five innings, has a 9.77 ERA in 15 2/3 innings this spring. He's allowed 21 hits over that span. Garcia is one of several pitchers in camp trying to win the final spot in the Padres' starting rotation.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.