Two years ago, just before his elbow crapped out for the second time, Nathan Eovaldi started experimenting with the pitch that would revitalize his career.

His repertoire, anchored by a four-seamer that routinely touched 100 mph, was already pretty deep, featuring a splitter, slider, and occasional curveball. But with his first foray into free agency looming - and his performance on the mound continuing to underwhelm - adding a cut fastball to complement his triple-digit heater couldn't hurt.

Tinkering, after all, is kind of his thing.

"I like to think of myself as a different pitcher each year," Eovaldi told theScore earlier this week. "Try and find a new weapon, or try and find something that's going to help me improve my game and continue to get better as the years go on."

The early returns were encouraging. Eovaldi, then in his second season with the New York Yankees, pitched to a 3.60 ERA across his first four starts after adding the new weapon to his arsenal in mid-July - promising results, to be sure, given he had spent the two weeks leading up to the All-Star break languishing in the bullpen on account of poor performance.

Then, just like it did during his junior year in high school, Eovaldi's ulnar collateral ligament blew out, necessitating a second Tommy John surgery. The rehab - performed under the auspices of the Tampa Bay Rays, who signed him to a one-year deal with a 2018 club option months after he had his UCL replaced - was arduous.

The return, so far, has been triumphant. Inarguably, this version of Eovaldi - rebuilt, and with a new approach on the mound - is the best yet.

His elite velocity returned post-surgery, but much of the success he has enjoyed since coming off the disabled list May 30 is a direct result of that cutter he started toying with two summers ago.

"It was real effective for me," he recalled. "The main thing was just getting hitters off my fastball with (it). I think coming back from the surgery this year, it was one of the pitches I didn't want to forget about, and I wanted to keep trying to improve on it just because of the success I was having with it."

Blessed with "tremendous arm speed," as Boston Red Sox assistant pitching coach Brian Bannister put it, Eovaldi throws his cutter 92.7 mph on average. No starter throws it harder, and only two relievers (Bryan Shaw and Tommy Hunter) do. Eovaldi uses it often, too, throwing his cutter nearly 31 percent of the time - more frequently than any starter (min. 1,000 pitches) other than CC Sabathia, Madison Bumgarner, and Blaine Hardy, all of whom are left-handed. Now, for the first time since abandoning his sinker in 2012, Eovaldi throws two discrete fastballs, each with its own unique trajectory, extremely hard, and with a similar frequency. It's working. Not only because a 93-mph cutter is exceedingly difficult to barrel up, mind you, but because it makes his 100-mph four-seamer that much more overbearing.

Year Cutter % Four-seam xwOBA Four-seam whiff % Cutter xwOBA 2015 - .373 6.8% - 2018 30.6% .333 12.4% .303

"At first, it just (worked) as a pitch that I could drive into the lefties or away to the righties," Eovaldi said. "And it's developed as one of the pitches where I can now backdoor to lefties and sometimes front door to righties."

He continued: "I think it's just kind of been a confidence pitch for me. If it doesn't break, then at least it's going to be hard, as opposed to if I'm trying to throw a slider and it backs up, it's kind of, you know, 85-88 (mph), just hovering right there in the middle of the strike zone. With the cutter, if I can get just a tiny bit of movement from it, it's going to be effective for me."

The overall results have been staggering. Through a dozen starts this season, Eovaldi - traded last month from Tampa Bay to Boston - owns career bests in virtually every statistical category, including ERA (3.38), ERA+ (121), WHIP (0.89), strikeout rate (22.6 percent), walk rate (3.3 percent), whiff rate (10.8 percent), opponents' batting average (.208), and expected weighted on-base average (.297). Take out one disastrous outing against the Minnesota Twins and his ERA shrinks to 2.47.

Prior to this season, excepting his 2011 rookie campaign, in which he threw all of 34 2/3 innings, Eovaldi had fashioned an above-average ERA, after adjusting for park effects, just once in his career. From 2011 through 2016, he was profoundly mediocre, managing a 4.21 ERA (94 ERA+) across 127 starts and seven relief appearances between the Yankees, Miami Marlins, and Los Angeles Dodgers while consistently (and confoundingly) putting up modest strikeout numbers that belied his elite velocity.

Now, he's giving up less hard contact than Luis Severino, Zack Greinke, and Blake Snell. In just 72 innings this year, Eovaldi has accrued more WAR (1.3) than Jon Lester and Steven Matz combined. The cutter, it cuts deep.

"Hitters aren't hitting it," he said. "They're not adjusting to it, so I'm going to keep throwing it until they start to make an adjustment."

He will, indeed. As the season has progressed, Eovaldi has only come to rely on the pitch more. His last time out, in fact, for the second start in a row, he threw more cutters than four-seamers. That night, he allowed only four baserunners over eight scoreless innings.

"He's not just letting it fly," said Bannister. "He has a purpose with it, and he has a very repeatable release point when he throws it. It kind of gives hitters fits because they think they're right on it and they miss it by an inch or two."

Ostensibly, as the July 31 non-waiver trade deadline crept closer, the Red Sox - an unstoppable behemoth that waltzed into the All-Star break winning at a .694 clip - were set in their rotation. Even with Eduardo Rodriguez newly injured, between American League Cy Young favorite Chris Sale, David Price, and Rick Porcello, Boston didn't need any major upgrades on the starting pitching front. Drew Pomeranz and Steven Wright would be back soon enough from their respective injuries.

Then, on July 25, less than 24 hours after Pomeranz got rocked at Camden Yards in his return from the disabled list, the Red Sox sent left-handed pitching prospect Jalen Beeks to Tampa Bay for Eovaldi, rescuing the resurgent right-hander (much to his surprise) from a meaningless second half and adding an impact arm to a rotation that, despite the injuries, ranked fifth in the majors in WAR (10.0) and park-adjusted fielding independent pitching (91 FIP-), and fourth in park-adjusted ERA (86 ERA-), at the All-Star break.

"I didn't think I'd be traded to the Red Sox," Eovaldi said. "Of all the teams that there was talk about, they had never been mentioned. But I'm definitely excited to be here and trying to contribute to this ballclub and help them try to win a World Series."

Already, his contributions have been sizable. In two starts with the Red Sox, Eovaldi hasn't allowed a run, first tossing seven scoreless frames in a redemption outing against the Twins on July 29, then limiting the Yankees to two singles, one double, and a walk over eight shutout innings five days later. Since his debut with the Red Sox - and absent any help from Rodriguez or Sale, who hasn't pitched since July 27 due to shoulder inflammation - Boston's starters have combined for a 3.39 ERA and limited their opponents to an MLB-best .199 batting average. Moreover, the Red Sox are 8-2 over that span, and head into Friday's series opener in Baltimore - which Eovaldi is slated to start - with an eight-game lead over the Yankees in the American League East.

Once everybody returns to health, in other words, watch out. This rotation will kill you five times before you hit the ground.

"There's a lot of diversity with the guys," said Bannister. "Sale has a unique arm slot. Eddie, prior to the injury, was throwing very well. Porcello is a right-handed sinkerballer. Eovaldi is throwing a lot of cutters at really high velocity. So I think it's a good mix and a good variety of arms, and they all bring something to table. What's fun is they all make each other better. They love to talk the game. They have a passion for their craft. And I think it's a group of guys that really has one goal in mind, and that's to win a World Series."

Irrespective of whether the Red Sox hoist the Commissioner's Trophy come November, though, Eovaldi's renaissance has huge implications for him, personally. After all, the 28-year-old will be a free agent this winter, and his newfound success - along with his relative youth and, thanks to his midseason trade, being ineligible for a qualifying offer - will likely make him one of the most highly sought after starters on the market. Really, after Arizona Diamondbacks left-hander Patrick Corbin, Eovaldi might be the most desirable free-agent starter.

Impending FAs

Name WAR ERA- FIP- WHIP xwOBA Age Patrick Corbin 4.7 77 59 1.04 .289 28 Charlie Morton 2.6 69 83 1.14 .288 34 Dallas Keuchel 2.5 86 89 1.24 .308 30 J.A. Happ 2.2 95 92 1.13 .309 35 Anibal Sanchez 1.4 70 91 1.05 .291 34 Gio Gonzalez 1.4 95 103 1.48 .334 32 CC Sabathia 1.3 82 103 1.31 .309 37 Nathan Eovaldi 1.3 82 94 0.89 .297 28 Lance Lynn 1.3 106 102 1.54 .327 31 James Shields 1.2 107 110 1.30 .354 36 Marco Estrada 1.2 109 110 1.28 .345 34 Garrett Richards 1.0 89 100 1.28 .324 30 Tyson Ross 0.7 115 113 1.33 .343 31 Matt Harvey 0.5 133 121 1.35 .360 29 Bartolo Colon 0.2 117 122 1.27 .370 45

Excepting Corbin, Houston Astros righty Charlie Morton is clearly having the best season among the starters from the upcoming free-agent class, but he also turns 35 shortly after the World Series and will almost certainly be attached to draft-pick compensation. Morton's teammate, Dallas Keuchel, is having a fine season, too, and the veteran left-hander has an AL Cy Young award on his resume, to boot. But he's also a touch seasoned, and his performance over the last three years (107 ERA+, 3.80 FIP) hasn't quite lived up to the standard set in his sensational 2015 campaign. Sabathia is old. So is J.A. Happ. Garrett Richards can't stay healthy. Matt Harvey is broken. Lance Lynn is mediocre. They're all dubious investments, this lot, is the point.

Absent a track record of sustained success, Eovaldi may be, too. Recency bias is a powerful force, however, and with his revamped repertoire - and a market increasingly disinterested in paying old dudes heaps of money for past performance - he may well be in for a massive payday this winter.

All of that can wait, though. First, there are outs to get. Many more cutters to throw before he sleeps, so to speak.

"I'm not thinking about that at all," Eovaldi said of free agency. "(My mindset is) focus on the things I can control, and that's going out there and taking the ball every five days and trying to get outs. I'm not thinking about the free agency whatsoever. When that comes, that'll be in the offseason and that's when I can start focusing on that, but otherwise, it's taking the ball every five days and trying to go out as long as I can and give the team the best chance to win."

Jonah Birenbaum is theScore's senior MLB writer. He steams a good ham. You can find him on Twitter @birenball.

(Photos courtesy: Getty Images)