On Sunday, MLB.com looked at hitters who improved the most from 2016 to '17 in select Statcast™ categories.
Now it's time to give pitchers the same treatment, examining which hurlers saw a boost in stuff (velocity and spin rate) and which induced more favorable contact.
Here are the results:
Average four-seam fastball velocity
Minimum 250 thrown in 2016 and '17

1. Tyler Chatwood, Rockies: +2.1 mph (92.7 to 94.8)
   
2. Felipe Rivero, Pirates: +1.9 mph (96.5 to 98.4)
   3 (tie). Raisel Iglesias, Reds: +1.7 mph (94.6 to 96.3)
   3 (tie). Chase Anderson, Brewers: +1.7 mph (91.6 to 93.3)
   
3. Corey Knebel, Brewers: +1.4 mph (95.9 to 97.3)
   This section excludes pitchers who moved from the rotation to the bullpen in 2017, as such a shift naturally tends to cause a velocity spike. For example, the D-backs' Archie Bradley saw his four-seamer jump from 93 mph as a starter in '16 to 96.3 mph as a reliever this year, when he emerged as a top bullpen piece for Arizona.
   Chatwood, who has toiled away in Colorado since 2012, is an intriguing free-agent option this offseason. In his second year back from his second Tommy John surgery, the right-hander bumped his overall average fastball velocity (including two-seamers) from a career-low 92.6 mph to a career-high 94.6 mph. Though Chatwood did make eight relief appearances, he reached as high as 98.1 mph in his 25 starts -- his best mark in that role since his 2011 rookie season.
   Iglesias was quietly dominant as Cincinnati's closer, with a 2.49 ERA, a 30.1 percent strikeout rate, a .576 opponent OPS and 28 saves in 30 chances. Factoring in sinkers, his average fastball shot up from 93.2 mph to 96.1 mph, while his opponents' slugging percentage on those pitches dropped from .358 to .322.

Average four-seam fastball spin rate
Minimum 250 thrown in 2016 and '17

1. Nate Karns, Royals: +181 rpm (2,210 to 2,391)
   
2. Jordan Lyles, Rockies/Padres: +159 rpm (2,080 to 2,239)
   
3. Knebel, Brewers: +158 rpm (2,284 to 2,442)
   
4. Rivero, Pirates: +150 rpm (2,315 to 2,465)
   
5. Chasen Shreve, Yankees: +143 rpm (2,388 to 2,531)
   Karns didn't pitch after May 19 this year and now is working his way back from thoracic outlet syndrome. But before that, he struck out 51 batters over 45 1/3 innings, with his four-seamer spin rate ranking 22nd highest among 179 starters who threw the pitch at least 250 times.
   Knebel and Rivero show up among the top five improvers in terms of both velocity and spin rate. Both young relievers ranked in the top 15 this season in four-seamer velocity and in the top 25 in four-seamer spin rate out of nearly 200 pitchers (minimum 500 four-seamers thrown).
   Both pitchers' four-seamers also were extremely hard to do damage to, yielding slugging percentages of just .274 for Rivero and .309 for Knebel. Batters also missed on 34 percent of their swings against Knebel's four-seamer, the fourth-highest rate in MLB (minimum 200 swings).

Average launch angle allowed
Minimum 200 batted balls in 2016 and '17

1. Dallas Keuchel, Astros: -5.0 degrees (3.4 to -1.6)
   
2. Chatwood, Rockies: -4.8 degrees (5.2 to 0.4)
   
3. Jose Quintana, White Sox/Cubs: -4.6 degrees (15.9 to 11.3)
   
4. Zach Eflin, Phillies: -4.4 degrees (15.3 to 10.9)
   
5. Zach Davies, Brewers: -4.1 degrees (10.3 to 6.2)
   Among pitchers who generated at least 200 batted balls in both 2016 and '17, Keuchel authored not only the biggest drop in launch angle, but also the second biggest in average exit velocity allowed (from 87.9 mph to 84.5 mph). The left-hander was the only pitcher this year to average a negative launch angle over at least 250 batted balls, his 68 percent ground-ball rate led MLB starters, and his expected wOBA allowed on balls in play -- based on quality of contact -- plummeted from .361 to .315.
   Along with his increased fastball velocity, Chatwood tied for third in lowest average launch angle and had the sixth-highest ground-ball rate (59.3 percent) among pitchers who generated at least 300 batted balls in 2017.

Hard-hit rate allowed (95+ mph exit velocity)
Minimum 200 batted balls in 2016 and '17

1. Danny Salazar, Indians: -12.8 percent (44.4 percent to 31.6 percent)
   
2. James Paxton, Mariners: -9.4 percent (40.9 percent to 31.5 percent)
   
3. A.J. Griffin, Rangers: -9.1 percent (40.4 percent to 31.3 percent)
   
4. Chris Rusin, Rockies: -8.6 percent (36.1 percent to 27.5 percent)
   
5. Andrew Cashner, Rangers: -8.4 percent (40.7 percent to 32.3 percent)
   Salazar can be something of an enigma, leading MLB starters (minimum 1,500 pitches) in swinging-strike rate (17.2 percent) and striking out one-third of the batters he faced, all while posting a 4.28 ERA. Yet there were some positive trends this year. In 2016, Salazar had both the highest average exit velocity (91 mph) and hard-hit rate among all pitchers who generated at least 200 batted balls. In '17, he improved to 33rd highest in average exit velocity (88.1 mph), and his hard-hit rate actually was lower than the MLB average of 33.3 percent.

Opponents batted a mere .223/.278/.324 off Paxton this year, as the left-hander showed he has top-of-the-rotation ability when healthy. His hard-hit rate put him in the top third of 139 pitchers who produced at least 300 batted balls, while his 2.8 percent barrel rate -- balls with the most damaging combination of exit velocity and launch angle -- ranked first in that group.
Cashner heads into free agency after posting a 3.40 ERA across 166 2/3 innings, despite a 1.3 strikeout-to-walk ratio. His performance on batted balls is what made those results possible, as Cashner also enjoyed the second-biggest drop in barrel rate, from 7.8 percent to 3.9 percent -- fourth lowest in MLB in 2017 (minimum 300 batted balls).