Lance Lynn's first visit to free agency last offseason wasn't exactly a happy one, and it wasn't all that hard to see why.
Hindered by the qualifying offer he had declined from St. Louis, along with underlying peripherals (4.82 FIP, 4.98 DRA, a below-average 19.7 percent strikeout rate) that hardly matched his shiny 3.43 ERA, Lynn had to wait until March to sign a one-year deal with the Twins. He had difficulty throwing strikes in Minnesota, and he carried a 5.10 ERA when he was traded to the Yankees in July. With the Yankees he had a 4.14 ERA in 11 games, including nine starts. Overall, his 4.77 season ERA was the highest of his career.
Now, Lynn, who will turn 32 in May, is back on the market again, and his 2018 wasn't exactly a strong platform year. He might yet find himself facing another long winter, because he's more of an "innings eater" than a "premium starter." But quietly, something changed with the Yankees. His strikeouts jumped up. His walks dropped by half. Forget the ERA. He was good in pinstripes. So what happened, and how much of it can he use to sell himself this offseason?
Let's look at the three different versions of Lynn, split between the three teams he's played on in the last two seasons. 
In 2017 with St. Louis, he had a below-average strikeout rate and a below-average walk rate.
In 2018 with Minnesota, he had a below-average strikeout rate and a below-average walk rate. (It's actually worse than that. At the time he was traded, he had the highest walk rate of any pitcher who had thrown 100 innings.)
In 2018 with the Yankees, he had an above-average strikeout rate, jumping from 21.3 percent to 26.4 percent. He managed to turn around those control problems so much that his worst-in-baseball walk rate actually became better than average, dropping from 13.2 percent to 6.1 percent. Forget the ERA for a minute. If there's nothing more important for a pitcher than getting strikeouts and avoiding walks, then he was a completely different pitcher with the Yankees.

That was reflected in his FIP, which dropped to 2.17, a top-five post-July mark. It was reflected in his Expected wOBA (a Statcast™ metric that accounts for quality of contact and amount of contact), which dropped from .329 with the Twins to .258 with the Yankees, a top-15 post-July mark among starting pitchers.
Absolutely no one thinks Lynn is one of the five or 10 or 25 best starters in the game, because he's not. We're talking about 54 1/3 late-season innings from a pitcher who has always been more "decent" than "great," and it's important to caveat that so many times that just turns out to have been a nicely timed hot streak. But something clearly changed, and it's our task to figure out what, because that informs a great deal about what to expect from him going forward.
Now, sometimes that's difficult. Sometimes you stare at lists of numbers trying to figure out what tiny thing changed to make a difference. But sometimes, local reporters make it extremely easy on you. In this case, it's the latter. On July 30, one day before the trade, and three days after one of the few starts where Lynn had been able to throw strikes with the Twins, the St. Paul Pioneer-Press gave us a push in the right direction. 
Lynn, under the tutelage of then-Twins pitching coach Garvin Alston, moved his position on the pitching mound during a late-July bullpen session on a road trip in Toronto.
According to Alston, Lynn moved a little closer to the third-base side on the pitching rubber. He also made slight alterations in the way his right foot contacted the slab -- "so he can get into his glutes a little bit more" -- as well as the way his left foot moved toward home plate.
Stride length wasn't the issue, Alston and his team determined, so much as the way Lynn's hips worked. "What it allowed him to do was make sure he was connected properly from his top half to his bottom half," Alston said. "That allows the ball to stay on plane just a little bit longer."
That should be easy enough to track with Statcast™ data. Did Lynn really move on the rubber in the way that he and Alston said? The answer is yes, noticeably so. With the Twins, Lynn was releasing the ball an average of two feet to the right of the center of the rubber. With the Yankees, that increased to 2.6 feet, so an increase of nearly half a foot.

So what does that mean? If pitching were as simple as "move closer to the side of the rubber," everyone would do it. It's not as easy as that, obviously, and pitchers tinker with this sort of thing all the time. We can look at Blake Snell, Chase Anderson, Brad Peacock and countless others as success stories after moving their mound positions, but there's also surely others with names you don't know who didn't improve after doing it. 
In Lynn's case, it's another Alston quote that's most interesting: "Now," the pitching coach said, "his pitches are doing what he expects them to do instead of being off the plate."
Let's see if we can see what he meant by that. Lynn famously throws a ton of fastballs, nearly 89 percent of the time, the highest rate of any regular pitcher. Nothing changed about his velocity, which was 93.7 mph with the Twins and 93.8 mph with the Yankees. His spin didn't meaningfully change, nor did his movement, nor did his pitch usage.
He threw more strikes, obviously, going from a 36 percent zone rate to a 40 percent rate, but the chief impact here is what happened against righties. Intuitively, this makes sense. If a righty pitcher moves to the right side of the mound, his pitches against righty hitters are coming in from a different angle, perhaps more on the hands. You can see the effect in his heat maps.

There are all sorts of numbers we could throw at you to express his improvement against righties, from the drop in slugging percentage (.372 with the Twins, .327 with the Yankees) to the drop in hard-hit rate (40.4 percent with the Twins, 34.7 percent with the Yankees), to even an increase in ground balls (46.4 percent with the Twins, 52 percent with the Yankees). Those are all meaningful, but if there's one thing you take away from this, let it be this insane nugget:
With the Yankees, Lynn struck out 38 right-handed hitters and allowed just one walk.
Another way to think about that is that 277 pitchers faced at least 50 righties from Aug. 1 through the end of the season. Lynn's 33.3 percent strikeout rate was 26th, essentially tied with Justin Verlander. His 0.9 percent walk rate was sixth, the best of any starting pitcher. The distance between those numbers -- 32.5 percent -- was 10th, behind only some of the true gods of the sport, like Chris Sale, Max Scherzer, Jacob deGrom, and Josh Hader.
(The story against lefties is less interesting. He allowed a .349 wOBA against them in 2017, a .353 with the Yankees in 2018, and .346 for his career. Nothing to see here.)

The lesson here isn't that Lynn should be expected to pitch like that over a full season. He shouldn't. It's not that a fastball-heavy righty with decent-but-not-elite velocity should be counted on to dominate. He shouldn't. You can't just look at the final two months and assume that's the pitcher you'll get, as though the years and years of information before that don't matter. It doesn't work that way. 
But it's also true that even in today's bullpen-heavy game, average pitchers who can eat up innings still matter. Maybe that's what Lynn is, a solid, low-upside back-end starter who adds value on a team with troubles finding enough arms, like Tampa Bay or Oakland. Maybe he's strategically deployed against right-handed lineups, if this change sticks.
The Lynn from a year ago wasn't that intriguing. The lack of interest in free agency wasn't terribly surprising. This year's Lynn may not look better, given his surface-level stats. But he's interesting now, in a way he wasn't last winter. A small change seems like it may have yielded big results. You'd better believe that's the story Lynn's people are pushing this winter, and it's going to be enough to get teams interested. He seems like a better bet now than he did then.