In line for a team-record seventh opening-day start, Hernandez struck out two and overcame brief control issues in the second when he gave up his lone walk.
A jovial, smiling Hernandez detailed his rigorous offseason conditioning program and his improved diet that's left him leaner ahead of his 28th birthday next month.
"I would love to get the ball in the playoffs," he said of the big void in his career.
Erasmo Ramirez, seeking to snag a rotation spot, followed with four innings. He allowed a run on four hits with three strikeouts.
Stefan Romero hit a solo homer in the first, and Brad Miller tripled and scored in the third for Seattle. Those were the only hits against Rockies starter Franklin Morales, who struck out four in four innings as he contends for the fifth spot in the rotation.
NL batting champion Michael Cuddyer went 2 for 3 for Colorado and scored on Jack Reinheimer's throwing error in the second.
Mariners: Manager Lloyd McClendon saw extra energy from Hernandez.
"Looked like he was a little more focused tonight," McClendon said. "He wanted to go back out (for a fifth inning), but we wanted to get Ramirez in."
Rockies: Manager Walt Weiss said he's in no rush to choose between Morales and Jordan Lyles for the final spot in the rotation with both pitching well.
"We'll stretch this thing out," Weiss said.
Rockies shortstop Troy Tulowitzki was walking without a limp in the clubhouse Friday afternoon, two days after being hit by a pitch on his left calf.
"The swelling has gone down," Tulowitzki said. "I've been in the training room all day trying to take care of it."
Tulowitzki took some swings Friday and will likely play in a game next week. But while the Rockies avoided a serious injury to their three-time All-Star, they remained tightlipped about the incident.
"I'd rather not comment on that," Tulowitzki said when asked if he thought Arizona's Wade Miley intentionally hit him.
Arizona slugger Mark Trumbo had been hit a half-inning earlier.
Mariners: Corey Hart started at first base and went 0 for 3 with a strikeout after missing the previous four days with a sore back. . Right-hander Taijuan Walker (shoulder) is scheduled to throw another bullpen session Sunday. . The Mariners are hoping the splint on the right middle finger of ace Hisashi Iwakuma will be removed next week. He's yet to throw a pitch this spring.
Rockies: Reliever Boone Logan threw batting practice Friday morning without incident. He's close to pitching in a game as he recovers from offseason surgery to remove bone chips in his left elbow.
MONTERO TO MINORS
Jesus Montero, who served a 50-game suspension to end last season for his role in the Biogenesis drug scandal, was demoted to Seattle's minor league camp.
Once a top catching prospect, Montero has moved to first base. The 24-year-old reported to camp overweight, offsetting his .310 average in 12 games.
"He worked his tail off. He just had so far to go, particularly coming in so heavy," McClendon said. "But he made tremendous strides. He probably made bigger strides than anybody in camp. But he's only halfway there."
Outfielders Xavier Avery and James Jones and shortstop Chris Taylor also were sent down.
Weiss is enjoying watching games this week with former Rockies star Larry Walker, who's at camp as a guest instructor.
"I talked about him being the most talented player I've ever played with," Weiss said. "He's probably the smartest player I've ever played with, too. . He sees things before they happen. And in between all that he's telling jokes."