GLENDALE, Ariz. -- Right away, you see it: Felix Hernandez is different. He has put on 17 pounds of muscle, but that's not quite it. Hernandez has cut his hair and doesn't play around with different hair dyes like usual. But that's not it either. He doesn't wear his socks up for the moment, he smiles a little less, and he pitches with force in February, something he hasn't done in years. But none of those things individually quite gets at what's different about Hernandez.

Instead, all of those things, combined, paint a picture: Hernandez isn't fooling around. Not this year. Not when the world begins to doubt him. That's what's different.

Hernandez is mad.

"Really?" Hernandez grunted at the home-plate umpire who called a ball on a curveball that looked an awful lot like a strike, especially from the pitcher's mound. He wanted that pitch. This matters because it is a Tuesday at the end of February, a cool day on a muddy field. And nobody can remember the last time Felix Hernandez cared about anything that happened in Spring Training, especially early Spring Training. What star veteran cares about Spring Training baseball? This has always been a time for King Felix to work out some kinks, stretch out the muscles, have fun.

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But this year is different. Hernandez is different. He has decided to rage against the fading light.

"His velocity was higher than I expected," said Seattle general manager Jerry Dipoto, who was sitting behind the plate Tuesday for the Mariners' 8-1 win over the White Sox.

Dipoto the scout was locked in.

"He was throwing 90-93," Dipoto said. "His fastball was sitting 91. He had nice sink to his pitches. He didn't throw a ton of changeups but the ones he did throw were really good. I mean, I couldn't be more pleased."

"Yeah, I was throwing 100 perecnt," Hernandez said when told about the sharpness of his stuff.

See, Hernandez is trying to do something that many people believe he cannot do: He's trying to reverse time. From 2009-14, Hernandez was probably the best pitcher in the American League, probably the second-best pitcher in the Majors behind only the incomparable Clayton Kershaw . He struck out 215-plus batters every year. Hernandez's strikeout-to-walk ratio was a brilliant four to one. He won an AL Cy Young Award and he could have won a couple more. King Felix was magnificent.

Then, in 2015, though he was just 29, Hernandez began fading. Oh, he still won 18 games and he still finished tied for the AL lead in shutouts, but everything fell off. Hernandez's ERA was a touch higher than normal. His strikeouts were down. Felix believers wanted to believe it was nothing, a momentary blip.

Last year, the roof caved in a bit. Hernandez defenders are quick to point out than an 11-8 record with a sub-4.00 ERA in the AL is hardly a disaster. But by the exalted standards of King Felix, it was not good. His ERA (3.82) was the highest it had been in almost a decade, and his 4.63 FIP -- the Fielding Independent Pitching number that breaks down a pitcher's performance based on strikeouts, walks and home runs -- was by far the worst of his career. Hernandez's right calf injury limited him to just 153 innings, his lowest total since he was a 19-year-old rookie called up in August 2005.

Worse than the numbers, though, were the unmistakeable signs of decline. Hernandez's velocity dropped significantly. He was reluctant to throw his four-seam fastball, relying instead on a sinker -- a sure sign of a pitcher getting older. His command was shaky; his strikeout-to-walk ratio, always stellar, was the less than 2-to-1 for the first time in his career. And for the first time, Hernandez began hearing criticisms about his training methods, his pitching style and even his commitment to being a great pitcher.

Needless to say, Hernandez didn't like it. He still doesn't like it.

"Everybody sees it," Dipoto said. "His teammates see it. There's a different fight to Felix. He's in great shape. And he's driven in a way that I think is different. I keep telling people, the demise of Felix Hernandez has been greatly exaggerated."

Why did Hernandez struggle last year? That's the real question here, because it gives the road map to how he comes back. There are numerous theories.

Theory 1: Lost velocity

According to Statcast™ numbers, Hernandez's average fastball velocity between 2015 and '16 dropped about 1.5 mph, down to 90.7 mph. There is a lot of talk about King Felix's lost velocity, and how that affects not only his fastball, but his devastating changeup because the gap between his fastball and changeup shrinks (last year, there was only a three mph difference between them).

This theory does lose a little bit of steam when you realize that last season the league only hit .181 against Hernandez's changeup and hitters didn't exactly tee off on his fastball either (the league hit .242 and slugged .385 against King Felix's fastball).

Theory 2: Hernandez wasn't getting as much movement down in the zone

When Hernandez is good, his pitches drop out of sight. "Some people just have this skill or this gift to make the ball move in the lower part of the zone," Dipoto said. "He just has that."

But Hernandez didn't have it as much in 2016. According to Statcast™, hitters barreled the ball more often in 2016 in '15. Meanwhile, they topped the ball into the ground much less often. Was that a function of less movement? Well, it's true that hitters absolute teed off on Hernandez's sinker, hitting .305 off it and slugging an absurd .543. That's 75 points of batting average and more than 200 points of slugging percentage compared to just two years ago.

But Dipoto and the Mariners believe it wasn't sluggish movement that hurt Hernandez as much as it was ...

Theory 3: Hernandez had command problems and got himself into a lot of bad counts

"When Felix got ahead in the count, even last year, he was as great as ever," Dipoto said.

There's something to this one. Last season, when Hernandez got ahead 0-1, the league hit just .195/.270/.293 against him. That tracks pretty close to what he did in his good years.

But when Hernandez fell behind in the count, the league hit him pretty well (.248/.379/.436). And because he never really had great command of his fastball, he threw fewer first pitch strikes than at any point since 2009.

"Strike one," Dipoto said. "It's huge for any pitcher, but it is especially big for Felix, because if he gets ahead in the count, you don't have much of a chance. He can expand the zone, he gets so much movement on his pitches. We have talked a lot about strike one."

Theory 4: Hernandez struggled with pitch selection

Here's a fascinating Statcast™ number to consider: In 2008, when Hernandez was young and raring to prove himself, he threw the four-seam fastball almost 70 percent of the time. In 2016, he threw fastballs 17 percent of the time. Hernandez has thrown very few four-seam fastballs the past three seasons as he adapts and becomes more of a finesse pitcher.

The Mariners want to see Hernandez throw more of those four-seamers; Dipoto was thrilled by how often he threw them in his first spring outing. They want to see him challenge hitters early in the count, maybe go a bit higher in the zone now and again, give hitters a different look.

When asked if he could have adjusted a bit, Hernandez shrugged.

"Maybe," he said. "Maybe not."

Theory 5: Hernandez was hurt

This seems to be Hernandez's theory, and it too has some supporting evidence -- on May 21, after nine starts, he had a 2.21 ERA, the league was hitting just .205 against him and so on. Then he had a terrible outing against Minnesota and supposedly hurt his right calf while stretching before his next game. After Hernandez came back from the injury, he had a 4.48 ERA in 15 starts, his strikeouts plummeted and the league's batting average jumped 50 points.

"I'm healthy," Hernandez. "I feel good. That's the important thing."

Once you get through the theories, you are back to the question: Can Hernandez turn back time? He's only 31, but he began in the Majors at 19 and so his arm has quite a bit more wear on it that the typical 31-year-old pitcher.

Still, Hernandez fights. To fight the lost velocity and movement, he has built muscle working out with the same trainer who helped Robinson Cano rediscover his power.

And as far as regaining his impeccable command and feel for pitching, well, there's a new seriousness about Hernandez. He insists that he's still playing with the same joy that has marked his wonderful career, but now there's a little bit of an edge too. Last September, King Felix tapped Dipoto on the shoulder and said, "I want to pitch for Venezuela in the World Baseball Classic."

And Dipoto said: "I think that's great!"

"I think I surprised him, but I love seeing a driven Felix Hernandez," Dipoto said. "I know this is strange, but I hope they go a long way in the tournament. I want to see Felix pitching in big moments. I think that's only going to help him prepare."

Speaking of big moments, Hernandez has never had his moment on the stage in October. He is probably the second- or third-best pitcher in Major League history -- along with Hall of Famers Ferguson Jenkins and Jim Bunning -- to never appear in a postseason game. And unlike Jenkins and Bunning, Hernandez has played in a time when one-third of the league makes it into the postseason.

Dipoto has made a few bold moves -- acquiring Jean Segura and Jarrod Dyson , for example -- to try and push Seattle into its first postseason in more than 15 years. The Mariners are now one of the more athletic teams in baseball. They should play great outfield defense. The middle of their lineup -- with Cano, Nelson Cruz and Kyle Seager -- matches up with just about any team in baseball.

"We would love to get Felix to the postseason," Dipoto said with a smile.

"Then again, Felix would love to get us there," Dipoto said. "People ask me sometimes, 'Is Felix still a No. 1 starter?' Well, I don't like to put labels. But I will say that when he takes the mound, everybody on the other team's bench knows who is out there. They still know."