Edwin Diaz was 22 years old when he unleashed a 100-mph fastball to strike out the second Major League hitter he faced, Indians center fielder Tyler Naquin . It was June 6, 2016. At almost that exact moment, Mariners general manager Jerry Dipoto received the following text message from Tribe president Chris Antonetti:

"What was that???"

Two pitches later, Diaz touched 101 mph, and at that point, Dipoto thought he might have the answer. Diaz, who hadn't pitched many games above Class A Advanced ball, had just become an important piece in Dipoto's reconstruction of the franchise.

Dipoto had made the decision earlier in that 2016 season to make Diaz a reliever, even though his staff was split on the matter. On one level, it made sense, given Diaz's thin build led to questions about maintaining his 93-95 mph velocity in the fifth, sixth and seventh innings of starts. In a short role, he had the potential to throw harder and dominate hitters for an inning or two at a time.

"You can't make a closer," Dipoto would say later. "Closers let you know who they are, and Edwin let us know pretty quickly."

Ten games, to be exact. That's how many relief appearances Diaz made at Double-A Jackson before Dipoto decided not to waste another pitch on Minor League hitters.

Two years later, Dipoto's decision has been validated again and again, especially this season, as Diaz has put together one of the great seasons any reliever has ever had.

Diaz leads the Major Leagues with 47 saves and has a decent shot at breaking Francisco Rodriguez's all-time record of 62 set in 2008. Rodriguez and Diaz both had 47 saves by their team's 122nd game.

Diaz has struck out 103 of the 228 batters he has faced in 60 innings. He's done it with a wicked two-pitch combination -- a fastball that averages 97 mph and a slider that sits around 89 mph. Both those numbers are near the top of the charts for American League relievers, according to Statcast™. Veteran Joaquin Benoit helped Diaz come up with a slider two years ago, and an offseason of tweaking has made it even better. According to Statcast™'s latest data:

• Diaz's 40.7-percent swing-and-miss rate is the best among 335 relievers who've generated at least 300 swings.

• His slider generates a whiff rate of 55.4 percent that ranks fourth best among relievers who've generated at least 100 swings on slider entering play Wednesday. Opposing hitters have batted .107 against that pitch.

• Diaz has generated 64 strikeouts on the slider, tops in the Majors among relievers.

There has also been an improvement in pitch tunneling, that is, giving Diaz's slider and fastball the same look out of his hand, giving hitters less time to react, according to Baseball Prospectus tunneling figures.

In a word, dominance. Looking back on it, the Mariners remember that the kid never seemed overwhelmed, that he believed he belonged.

"It was his first big league game, but you would've thought it was his hundredth," former Seattle bullpen coach Mike Hampton said later.

The Mariners had first seen the confidence in 2015, when the coaching staff for his Class A Advanced team gave the pitchers a quiz about how to pitch opposing hitters. Diaz's answers lacked specifics.

"This guy can't hit me," he said.<p.> "I'm going to throw it right by him."</p.>

On Aug. 2, 2016, in his 25th appearance, Diaz, in his rookie season, was handed the baseball in the ninth inning for the first time. He's been there since, making good on 99 of 110 chances, including a scoreless 12th inning in a 2-0 victory over the A's on Wednesday.

The 99 saves are 10 more than any other closer since the day Diaz converted his first one ( Kenley Jansen has 89). If there's a concern, it's workload. He made his 60th appearance on Wednesday, and Mariners manager Scott Servais says he's managing those the best he can.

That's not easy given the tight AL West race Seattle finds itself in. Last weekend in Houston, Diaz collected saves in the first three games against the defending champions, leading Servais to plan a day off for the final game on Sunday.

But when the Mariners took the lead in the top of the 10th inning, Diaz had already informed Servais that he would be pitching the bottom of the inning. He finished off the Astros in 10 pitches to become the first reliever in 14 years (Joe Nathan) to get four saves in a four-game series.

Days off are tough to find for a team that has played 63 games decided by one or two runs. They've finished 46-17 in those games, and Diaz has been a big part of that success.

"He's been as big a contributor to what we've done here as anybody," Servais said. "He has been the constant at the back end that has allowed us to win all those games."

Even more impressive is that Diaz has been at his best in the closest games. His 24 one-run saves have tied former Dodger Eric Gagne for the most in history and are the biggest reason Seattle is 60-0 when leading after eight innings.

Diaz has become so efficient that he needed only 46 pitches to collect those four saves in Houston last weekend. Since blowing a save against the Rays on June 1, he has converted 27 in a row and allowed one earned run in his past 21 appearances.

Diaz seems certain to become the 17th reliever to collect 50 saves in a season. In Spring Training, Servais promised to get a haircut similar to his in exchange for 50 saves. That would be sides shaved with a carved lightning bolt.

"I'm aware," Servais told reporters. "Guys are starting to talk about barbers and things like that. I'm OK with that."

Spoiler alert: He's more than OK with that. It might be the happiest haircut he has ever had.