Hernandez (3-6) allowed three runs over the first three innings before settling into a groove that saw him retire the final 14 batters he faced, as he struck out eight and walked one while getting a lot of mileage out of a well-placed fastball and knee-buckling curveball.
This was, Hernandez insisted afterward, the result of Chaves' video work that turned up a slower delivery that the right-hander used last season when he posted a 2.67 ERA. By picking up his front leg slower, Hernandez stayed balanced on the mound.
"From the beginning of the game, I could see a difference in my pitches," said Hernandez, who had allowed a combined 12 runs on 18 hits in his last two starts. "I could see batters trying to get out of the way."
Many of Hernandez's problems this season -- he came into the game with a 5.84 ERA -- had to do with a lack of command on his fastball that some believed was a result of him rushing his delivery and, subsequently, falling off the mound.
Hernandez seemed to rectify both against the Twins and, by keeping his front shoulder closed -- something else he has been working on -- it allowed him to have a better break on his curveball.
"It was positive, his balance was better," Chaves said. "I'll take that any day."
So will the Mariners, who had their hands full with another 20-something pitcher who, like Hernandez, showcased some nasty pitches.
Minnesota starter Francisco Liriano (3-0), just 22, allowed four hits over five scoreless innings with six strikeouts and one walk. A converted reliever, Liriano is still working on building his arm strength, which explained his early departure after 82 pitches.
Looking much like a clone of teammate and fellow left-hander Johan Santana, Liriano worked quickly, using his fastball, slider and changeup to work his way through the Mariners' lineup.
"He's tough," Richie Sexson said. "You don't know what he's going to do. It's like he just grabs the ball and throws it. Those kinds of guys are tough to hit."
Hitting has been a problem for the Mariners lately, as they stretched their consecutive scoreless-innings streak to 21 before breaking through for a run in the seventh inning.
It looked like that streak would end much sooner, when the Mariners loaded the bases with no outs in the fifth inning as Liriano looked like he was starting to tire.
Adrian Beltre and Kenji Johjima opened the inning with singles, and Willie Bloomquist walked to load the bases. Liriano then fell behind in the count to Seattle's No. 9 hitter, Yuniesky Betancourt.
"Then he got tough again," manager Mike Hargrove said.
Liriano recovered to strike out Betancourt on a nasty slider down around his ankles for the first out.
Ichiro Suzuki then lined a ball into shallow center field that Torii Hunter got a good break on. Hunter made a shoestring catch and, noticing that Johjima had wandered too far off second base, threw behind the runner to complete the double play.
"Bases loaded and nobody out, you have to get at least one run out of it," Hargrove said. "That's a little frustrating. [Johjima] can't get that far off the bag."
A second mistake on the bases took some of the steam out of the only inning that Seattle scored in, as Beltre got too far off third base after Betancourt's RBI single in the seventh inning. Beltre was caught in a rundown and tagged for the final out.
This wasn't the way Seattle wanted to start its six-game road trip to Minnesota and Texas. But Hernandez's outing -- thanks to some keen video breakdown by his pitching coach and practical application on his part -- managed to provide the team one bright spot.
"Hernandez is filthy," Hunter said. "He settled down after the first two, three innings and he was nasty. I never faced him before. I was hurt last year when [the Twins] faced [the Mariners]. I wish I could talk to him and say, 'Hey, I need your autograph,' because he's going to be a superstar."