Trevor May isn't a flashy free agent on the level of a George Springer or Trevor Bauer or the other big names in the Mets' sphere of interest, but he should be a valuable one.

The 31-year-old righty reliever, with whom the Mets reportedly agreed on a two-year deal on Tuesday, is coming off a 2020 season in which he struck out nearly 40% of the batters he faced and averaged 14.66 strikeouts per nine innings, ranking sixth among relievers in K/9 and 11th in strikeout rate. He'll be a welcome addition to a Mets bullpen that always needs it.

May's strikeout numbers were good coming into this year -- he had an 11.05 K/9 and 29.7% strikeout rate in 2019 -- but now they're great. Here's how he turned into a strikeout artist.

He's throwing faster fastballs, and higher fastballs

May has been building up velocity since he came back from Tommy John surgery in 2018, and it's a big spike -- more than two full mph from 2018-20.

May's avg. 4-seam fastball velocity by season
2016: 94.5 mph
2017: Did not pitch (Tommy John surgery)
2018: 94.0 mph
2019: 95.5 mph
2020: 96.3 mph

Increased fastball velocity is obviously good. May is also taking advantage of his faster fastball by elevating it in the strike zone, and that's even better.

May's avg. fastball height by season
2016: 2.82 feet -- 52.8% of fastballs elevated (upper third of zone or higher)
2018: 3.05 feet -- 63.7% of fastballs elevated
2019: 2.87 feet -- 56.5% of fastballs elevated
2020: 3.27 feet -- 68.7% of fastballs elevated

This season, May threw more high fastballs than ever before. His fastball is getting to the hitter more than five inches higher than it was in 2016, and while he was barely throwing half of his fastballs up in the zone before his surgery, he's now elevating more than two thirds of them.

Hitters whiffed on nearly half of their swings against May's four-seamer in 2020. They couldn't catch up to his new high heat.

Highest 4-seam fastball whiff rate in 2020
1) Trevor May: 46.9%
2) Yu Darvish: 42.3%
3) Edwin Díaz: 41.1%
4) Chris Stratton: 39.1%
5) James Karinchak: 39.0%
Of 209 pitchers with 75+ swings vs. their 4-seamer

He's throwing more sliders, and sharper sliders

Like a lot of the other nasty pitchers in the game today, May has developed the wicked combo of elevated four-seamers coupled with down-breaking sliders. He traded in his curveball for that slider as his primary breaking ball, tripling his usage from just a few seasons ago while scrapping the curve in 2020 after it got crushed in '19.

His slider is better now, too. May has added almost 10 inches of vertical movement to his slider from 2016 to now, which has transformed it from basically league average to one of the harder-dropping sliders around. He now gets more drop vs. average than 90% of pitchers.

May's slider usage by season
2016: 8.7%
2018: 10.7%
2019: 14.5%
2020: 32.6%

Vertical movement on May's slider, 2016 vs. 2020
2016: 31.3 inches of drop | +0.1 inches vs. MLB avg.
2020: 40.7 inches of drop | +4.5 inches vs. MLB avg.

The slider May throws is a straight down-breaking one; it doesn't have a lot of horizontal break. Neither does his fastball, which is a true four-seamer. But his four-seamer only drops 12.8 inches as it carries through the upper part of the zone, while his slider drops an extra two-plus feet. So they work very well together. When you add in his improved changeup location -- May's third pitch was all over the place in 2019 but more tightly concentrated on the glove side of the strike zone in 2020 -- you can see how May ended up with all those strikeouts.

The three pitches May throws look a lot alike until they reach the point where the hitter has to commit to a swing, at which point they split apart from each other. May wouldn't have been able to pile up his 2020 strikeout numbers if his repertoire wasn't all in sync.