Seattle (85-77) finishes in third place in the AL West, completing the biggest one-season turnaround in the Major Leagues this season.
And Hernandez will finish tied for the Major League lead with 19 wins, the most by a Mariner since Jamie Moyer won 21 in 2003.
What's not known is where Hernandez will wind up in the Cy Young voting and whether Griffey, who has been mum on the issue of retirement to this point, will be back for another year.
Hernandez doesn't seem to care a whole lot one way or the other about the Cy Young.
"It's not about me. It's the voters and everything," Hernandez said. "If it happens, it happens. Next year is another year. I feel pretty good about my season, so that's the most important thing."
It would be hard for the rest of the Mariners to not feel good about their season, too, considering the 101-loss 2008 team and the divisiveness that had taken over the clubhouse. There was no trace of that in 2009, as Griffey and fellow veteran Mike Sweeney brought the levity and leadership that this team so desperately lacked one season ago.
And it didn't stop once Sunday's game was over. Sweeney snuck through a throng of reporters talking to manager Don Wakamatsu afterward, slamming an ice cream pie in the manager's face and yelling, "We love you, Skip!"
The entire room broke into laughter. But just seconds prior, Wakamatsu showed a rare emotional side. That was likely due to what had happened in the eighth inning, when Griffey singled up the middle, then was given two separate standing ovations as he was lifted for a pinch-runner and doffed his helmet on his way back to the dugout.
It could very well have been the last hit of his big league career, one that has included 630 home runs, 19 of those coming this season.
"It was probably the most nervous and emotional roller coaster I have ever been on as a ballplayer," Griffey said of his final at-bat. "You never know when it will be your last."
Nobody does, still. But everyone in attendance treated it like it was.
"I don't know, in the years that I've been in this game, if I've been as emotional as I was when Griffey came off and came through that dugout," Wakamatsu said. "It felt right."
Hernandez, who threw 120 pitches in his previous outing and tossed 107 on Sunday, struck out six and checks in with a 2.49 ERA. That's the fourth-best mark in franchise history.
"To get his 19th win of the season on the last day is awfully befitting and emotional," Wakamatsu said. "To see him start out in Spring Training and to go as far as he has and matured and become such a dominant pitcher, as a manager it's a joy to watch. It took him to 120 pitches his last start and he was on fumes today, and he went out and did it again for us."
Texas got to Hernandez with an unearned run in the fifth, when Craig Gentry hit an RBI groundout. Two more RBI grounders in the seventh after the Rangers put runners on second and third with nobody out would cut the Mariners lead to 4-3, but the bullpen picked up Hernandez.
David Aardsma recorded his 38th save to finish tied for fourth in the AL.
The Mariners dealt the deciding blows in the bottom of the fifth with runners on first and second, when Franklin Gutierrez and Jose Lopez hit back-to-back doubles with two outs to drive in three runs.
The lead held, and the Mariners took a 10-minute lap around the outfield afterward, tossing baseballs to fans and waving goodbye after a season that was likely better than anyone thought it would be.
"I've asked these guys to come every day, be prepared to play and play hard, and they did it to the last day," Wakamatsu said. "It's a tribute to how hard these guys have worked since Day 1, and I'm awfully proud of them."
Fittingly, in the season's final game, there was plenty to be proud of.