There are a few different ways I could begin this post, and I can’t settle upon a best one, so you’re going to get them all. Prepare for a blitz of introductions. Jason Grilli was the fourth overall pick in the 1997 draft, and he was sent from the Giants to the Marlins in a trade for Livan Hernandez. He made his big-league debut for Florida in 2000, when he was 23 years old, and as a starter he worked 6.2 innings. In that one debut start, Grilli allowed more baserunners than he’s allowed so far in 2013 as the Pirates’ closer. As of Wednesday, he’s up to 16 saves.

Moving on. Every year, a handful of pitchers try to come back from existing completely off the radar. Most of them try to return and fail, but sometimes they succeed and make for improbable stories. A few years ago there was Ryan Vogelsong, and now there’s Scott Kazmir, who everyone previously assumed was never to be heard from again. Another guy trying to come back is Jeremy Bonderman, with the Mariners organization. He’s presently in Triple-A, and while he might not make it back to the majors, at least he knows a part of him is alive and well at the highest level. Because it was Bonderman who gave Jason Grilli some invaluable advice on developing and harnessing a slider.

Changing course. I might just make this whole post a disjointed assortment of introductions. Grilli landed with the Pirates in the middle of 2011, after he’d been pitching in Triple-A for the Phillies. The Phillies decided they didn’t have a spot for him in the bullpen, despite his statistical performance, so they allowed him to leave, and Grilli looked forward to a reunion with Clint Hurdle. While the Phillies did have a good bullpen that year, it wasn’t solid from top to bottom, and shortly thereafter they released Danys Baez. So they have that to regret. But while that looks like a major mistake in hindsight, Grilli’s move to Pittsburgh was such minor news at the time that Grilli broke it himself:

Black & Yellow! Black & Yellow! Black & Yellow! Cannot wait to join the new squadron. — Jason Grilli (@GrillCheese49) July 20, 2011

And Grilli’s fallen in love with his situation. You can observe that here:

For the first time in career, he sees people in the stands wearing his jersey. The sight of a 40-foot banner outside PNC Park with his face on it stuns him. “I’ve never felt this kind of love from a city,” Grilli said.

You can also observe it in the fact that Grilli stayed with the Pirates after being a free agent last offseason. He signed for two years and $6.75 million, turning down bigger offers from elsewhere. Grilli’s the closer in Pittsburgh, and he’s a nearly unhittable one, for cheap. Last October the Dodgers signed Brandon League to a three-year extension worth $22.5 million. There’s already talk of replacing him as closer with Kenley Jansen. League, all year, has seven strikeouts. Grilli has six strikeouts since Sunday.

I don’t know if I’ve yet made it clear that Jason Grilli is completely dominant. I know Dave Cameron likes to look at the leaderboards covering the past calendar year. Over the past calendar year, Grilli has struck out 38% of opposing batters. He’s posted a 2.11 FIP, slotting him between Jansen and Aroldis Chapman. Just this season, Grilli’s got an FIP of about half a run. He’s got baseball’s highest strikeout rate. He’s got CC Sabathia‘s walk rate. If you add up his ERA-, FIP-, and xFIP-, you get Tim Lincecum’s career ERA-. He’s getting paid less than Yasiel Puig.

And making it all the more incredible is the course of Grilli’s development. Recall that he was drafted in 1997. Know that he’s 36 years old. Below, Grilli’s major-league strikeout rates since 2005, excluding 2010, which he missed because of a leg injury:

2005: 7.9%

7.9% 2006: 11.5%

11.5% 2007: 17.6%

17.6% 2008: 21.4%

21.4% 2009: 23.1%

23.1% 2011: 26.4%

26.4% 2012: 36.9%

36.9% 2013: 43.3%

Granted, between 2005 and 2006, Grilli shifted to the bullpen. Granted, strikeout rates have been going up league-wide. But in case that doesn’t make Grilli’s progress clear, how about we look at this in a different way? Pitchers with similar strikeout rates to Grilli’s, by year:

As he’s gotten older, Grilli has figured out how to strike batters out. And his walks have actually gone down, despite the increase in deep counts. Jason Grilli has been climbing for a long time, and now he’s pitching like an All-Star closer for a Pirates team that might finally snap one of the most ignominious streaks in professional sports. The secret? There is no one secret, and if you ask Grilli, he’ll say that he just needed to get a good chance. He’s always had a live fastball, and years and years ago he ditched a curve in favor of a slider, which he still leans on today. This is what that slider looks like:

Though Grilli is a fastball/slider righty reliever, he’s able to succeed against lefties, allowing him to serve as an effective closer. And while I can’t prove causation, it’s interesting to note that Grilli’s leap forward in 2011 correlates with a change in his slider’s movement. Thanks to Texas Leaguers, check out Grilli’s pitches between 2008-2009, and then his pitches since 2011:

Ignore the slider/curveball distinction in the second graph. They’re all the same pitch. According to PITCHf/x, Grilli’s fastball now has about the same movement as it did in 2009. But his slider has three and a half more inches of horizontal movement, and four and a half more inches of sink. One notes that, between 2008-2009, Grilli threw 61% strikes. Since joining the Pirates, he’s thrown 66% strikes, generating a lot more swings. It stands to reason that Grilli’s different slider has made both his slider and his fastball better, and it also stands to reason that Grilli has made some improvements to his command. He’s still not a guy who consistently hits his spots, but the quality of his stuff is such that he can survive and thrive. His fastball spends a lot of time above the belt, which can be a dangerous area, but also a swing-and-miss area. Grilli’s technique these days is simple, but he’s mastered it, allowing him to become one of the premier relievers in the league.

It would be easy to use Jason Grilli as an example of why you shouldn’t pay too much for a closer. Better to use Brandon League as an example to demonstrate the same thing. That frees up Grilli to be used as an example of why baseball is amazing. About 16 years ago, Grilli was drafted in between Troy Glaus and Vernon Wells. And wouldn’t you know it, but he’s reaching his potential.