"In 2019, his age-24 season, Lucas Giolito is likely going to make the All-Star team and could even receive Cy Young votes." That wouldn't have been a particularly surprising statement back in 2012, when the Nationals made him the 16th overall pick in the Draft, two slots ahead of Corey Seager.

It would still have been believable in early 2016, when he was considered the third-best prospect -- and best pitching prospect -- in baseball at MLB Pipeline. It would still have applied in December 2016, when he was the centerpiece of the trade that sent Adam Eaton from Chicago to Washington.

It would have been a little more surprising in 2017, when he put up a 4.48 ERA in Triple-A and struggled to miss bats in a few starts in the Majors. It would have been downright stunning in 2018, amid questions about his declining velocity and a stat line that legitimately made him one of the worst regular starters in baseball.

In 2019? Giolito has a 2.54 ERA, seventh-best among qualified starters. He's got some of the largest yearly jumps in strikeout rate and velocity. He's become the ace the White Sox had long hoped he would be, and it doesn't seem like a mirage. How does this even happen?

Giolito signed with the Nationals on July 13, 2012, about a month after the Draft, and got into exactly one game that summer before injuring his elbow and requiring Tommy John surgery. That wasn't exactly a huge surprise; Giolito had missed much of his senior season of high school with an elbow sprain, and the concerns about his health had caused him to drop to the Nationals at No. 16.

He returned late in 2013, and generally performed as expected at various levels of the Nationals system, then got into six late-season games, including four starts, for Washington in 2016. It didn't go well. It's not that the 6.75 ERA in 21 1/3 innings was all that meaningful, because that's a small sample for a 21-year-old. It's that he had an 11/12 K/BB mark in that span. It's that of the 596 pitchers who threw 20 innings that year, only 15 had a lower strikeout rate than his 10.9%. Only 10 had a worse strikeout-to-walk rate.

And, in those early days of Statcast, it was that his fastball spin rate was unexceptional, providing clues that the fastball might not be the dominating pitch that his reputation suggested it might be. Giolito was known for touching 100 mph in high school, but in 2016, his 94.0-mph four-seam velocity was tied for 138th of the 378 pitchers who'd thrown 200 four-seamers. But his spin rate of 2,064 rpm was 354th of those 378, or, if you prefer, 23rd-lowest.

As we've come to learn, low fastball spin correlates well to sink, while high spin can often give the "rising fastball" effect, which works better for missing bats. That might have been why, in 2016, Giolito's swing-and-miss rate on his fastball was only 9.1%, the ninth lowest of 365 pitchers to get 100 swings on their four-seamers. Again, this came in a small sample, but it was a clear warning sign about his ability to dominate with the pitch.

That's why, when Giolito was traded to the White Sox that winter, there were more than a few questions about what Chicago was actually getting. At FanGraphs, months before the trade, Jeff Sullivan -- currently an analyst for the Rays -- wrote "the stuff wasn’t … quite … there, not as advertised," then the day before the trade followed up by writing that Giolito "has also been a declining asset. Since the end of July, Giolito kept on not retiring Major League hitters. He’s a 22-year-old top prospect, but there are more questions about him than ever."

Fresh off the unimpressive debut and lack of spin or whiffs, we noted something similar.

Even in 2017, when Giolito posted a shiny-looking 2.38 ERA in seven starts for Chicago, the underlying numbers suggested nothing had changed. His strikeout rate had dropped from his 2016 debut, and his walk rate had nearly doubled. No pitcher in baseball who threw 40 innings that year had a larger gap between his ERA (2.38) and FIP (4.94), a number derived from strikeouts, walks and home runs. It suggested that the nice ERA was something of a mirage.

It was. Giolito's 2018 season was nothing less than a disaster. His 6.13 ERA was the third worst, minimum 150 innings, in the entire history of the White Sox, dating back to the birth of the American League in 1901. His once-vaunted fastball had backed up to a mere 92.4 mph, only 230th of 363 pitchers who had thrown 200. Remember when we talked about how his four-seamer wasn't missing bats in 2016? It wasn't in 2018, either; he was 301st of 352 who induced 100 swings.

Obviously, much of that has changed. Now that we've made it through the litany of negative things that happened, let's look at all the ways in which Giolito has improved in 2019, among pitchers with 100 innings last year and 50 this year.

• ERA down by 3.59, from 6.13 to 2.54 (largest drop in MLB)
• K% up by 13.8%, from 16.1% to 29.9% (largest jump in MLB)
• BB% down 3.9%, from 11.6% to 7.7% (second-largest drop in MLB)
• HR/9 down by .087, from 1.40 to 0.53 (largest drop in MLB)
• Average down by .063, from .248 to .185 (third-largest drop in MLB)

Sure, some of this is because he was starting from such a low point that it was always going to be easier for him to improve in a way that, say, Max Scherzer or Justin Verlander couldn't. But still, Giolito has turned himself from a pitcher who didn't really belong in a Major League rotation into one who seems like a star in less than a year. How?

It started with a ton of hard work, apparently. Just look at this collection of quotes from Giolito from February.

Here he is telling MLB.com's Scott Merkin about his new training methods, specifically the core velocity belt. (You can see video of him using the device here.)

“Basically, it’s a tool that I started using this offseason just for my normal towel drill work, certain gym work, slide board stuff, med ball stuff,” Giolito said. “When I put it on, it basically wraps around your legs, your waist. You hook on with rubber bands, and there’s different ways you can do it, which kind of moves the resistance, or it will do the opposite and will help you hit the position you are trying to hit.

Here he is telling Scot Gregor of the Northwest Herald about improving his mental approach.

“I did a – it’s called a neurofeedback program where basically they read your brain waves. You work to build better neural pathways. Everyone is different. For me, it was about focusing on breathing, being confident at all times, just things like that where I kind of put it all together on the mental side."

And in a long chat with James Fegan of The Athletic, Giolito detailed how he was working on his mechanics, including using weighted baseballs and technology like the Rapsodo and, somewhat unintentionally, shortening his arm action from last year's much longer motion. You can see the difference pretty clearly in this 2018/19 comparison GIF.

"He’s changed his delivery or his arm action a little bit, which got him in the strike zone," said Houston manager AJ Hinch after Giolito shut out the Astros, 4-0, in May. He's right; last year, Giolito threw pitches in the zone just 47.2% of the time, and this year, it's 52.4%. That's reflected in the fact that in each of the previous three years, he was ahead in the count on only about a quarter of pitches, and this year, that's up to nearly 33%.

OK, so: Giolito put in a ton of work this winter, physically and emotionally. It wouldn't be the first time a pitcher declared himself to be in better shape entering a season. It wouldn't even be the first time Giolito looked like he was a new man in Spring Training, because we were hearing about all of his changes back before his brutal 2018, too.

The changes, and the hard work, are all well and good, and the results have been clear. But what has actually come of them? This is where it gets good.

1) He's throwing his four-seamer harder

Giolito is probably never going to be the Noah Syndergaard-esque flame-throwing velocity monster you might have envisioned in high school, but that velocity dip we referred to above was going to make it difficult for him to succeed.

He's still not Scherzer or anything, of course. But it's up, and it's better.

Right now, there are 149 pitchers who have thrown at least 200 four-seamers in both 2018 and '19. Only five of them have added more velocity than Giolito's +1.5 mph, and two of them aren't exactly fair comps, since Ian Kennedy moved to relief, and Drew Pomeranz had injury problems last year. The fastball, in turn, has seen far better results. Velocity isn't everything, but it matters.

2) He finally stopped throwing that sinker.

Giolito threw his two-seam, sinking fastball 20.5% of the time in 2018. He's thrown it zero percent of the time in 2019. Not only was it his second-most used pitch last year, it ascended to his most-used pitch in September, when he threw it 35% of the time ... and was rewarded with a 9.27 ERA, the seventh-worst month of any pitcher who threw at least 20 innings in a month in 2018.

Baseball, as a whole, has moved away from the sinker, and Giolito's wasn't strong. "Don't throw your worst pitch" is simple advice, but effective.

3) He's using his changeup more.

Instead, he's using his changeup 24.4% of the time, up from 15.7%, and it's been an effective one, allowing a .127 average and a .190 slugging percentage. It's been the third-best changeup in baseball, actually, behind only Hyun-Jin Ryu and Cole Hamels.

It's not that it's the best changeup in terms of movement or velocity or anything, really; when Alex Gordon saw it at the start of the year, his reaction was that "it’s not the best changeup, but he has really good arm action, so it kind of keeps you off balance."

This goes back to the shortened arm action we discussed above, which is somewhat difficult to quantify, but easy to see in terms of what it does. Look at how much more consistent Giolito's release point has been on the pitch this year, as compared to last.

4) He's burying his slider, and it's become an elite pitch

Last year, Giolito's slider was his fourth-most-used pitch, and even this year, he's using it only 13% of the time. But it's been a truly dominant pitch, especially if you look at the top of the slider leaderboard in terms of lowest wOBA allowed:

.065 -- Ryan Pressly, HOU
.074 -- Lucas Giolito, CWS
.092 -- Justin Verlander, HOU

Pressly just set a record for most consecutive scoreless outings. Verlander is Verlander. And this isn't Giolito's primary pitch or anything near it.

Against righties, this has become his main putaway pitch, coming out 35% of the time that he's ahead, and he's doing something differently here, too. In 2017, only 47.3% of his sliders were "low," or less than two feet off the ground. In 2018, 51.6% were low. This year, 58.5% are low.

There's so much more than this, really. There's evidence that he's moved closer to the first-base side of the rubber. There's evidence that he's quickened his pace, taking 24.8 seconds between pitches after needing 25.6 seconds the year before, and that the shortened arm action has simply improved his deception. There's also the fact that he's simply so young; Giolito doesn't even turn 25 until July. (Compare that to, say, Jacob deGrom, who made his Major League debut a month before his 26th birthday.)

There's not one magic reason for Giolito's improvement, because there never is. It just shows there's never one straight path to success. Sometimes, a highly touted first-rounder arrives and dominates immediately, like Stephen Strasburg. Sometimes it takes years, or never comes at all. Giolito isn't dominating in exactly the way we might have thought when he was drafted seven years ago. He's a different pitcher now. He's a much better one, too.