Every major league pitcher’s career is built from the raw materials of his pitch repertoire. Whether fastball, cutter or curve, all of a hurler’s offerings have to work together to help him confuse hitters and evade bats. And with a couple of months of 2016 PITCHf/x data in the books, I wanted to find out which players’ individual pitches have improved the most relative to last year.

First, I had to quantify “improvement.” For each pitch type I looked at — four-seam fastball, slider, curve and change-up — I built a model to predict how much the pitch’s run value depended on its velocity versus spin rate. Then I looked at all the pitchers who had thrown more than 500 pitches each in both 2015 and 2016 and calculated the change in value for each pitch type in a pitcher’s arsenal, based on how its velocity and spin changed.

Most pitches stayed close to their 2015 predecessors. For instance, the correlation between 2015 and 2016 for velocity on four-seam fastballs was 0.9, and the average velocity changed by only three-quarters of a mph, so it’s rare for a pitcher to completely reinvent a pitch from year to year. But whether because of injury or even a new grip, some individual pitches did change substantially. Here are the biggest year-over-year improvements — and declines — for each pitch in 2016, starting with fastballs:

Fastballs

LARGEST IMPROVEMENTS LARGEST DECLINES PITCHER CHANGE/100 PITCHER CHANGE/100 1 Mike Montgomery -0.50 1 Mike Leake +0.56 2 Cody Anderson -0.42 2 Taylor Jungmann +0.41 3 David Phelps -0.36 3 CC Sabathia +0.41 4 Kendall Graveman -0.31 4 David Price +0.41 5 Danny Duffy -0.30 5 John Danks +0.39 6 Jesse Hahn -0.30 6 Dallas Keuchel +0.36 7 Hector Santiago -0.27 7 Chris Sale +0.34 8 Martin Perez -0.26 8 Jacob deGrom +0.29 9 Doug Fister -0.23 9 John Lamb +0.29 10 Jhoulys Chacin -0.22 10 Marcus Stroman +0.29 Biggest changes in four-seam fastballs from 2015 to 2016, by change in runs per 100 pitches Negative run values are better — the pitcher is allowing fewer runs. Source: Pitchinfo

When pitchers modify their repertoires, they tend to trade speed for spin, or vice versa. But in his transition from starter to bullpen ace, Seattle Mariners thrower Mike Montgomery has managed to add both speed and spin to his four-seam fastball this year, rapidly making it one of the most fearsome offerings in MLB.

Montgomery’s heater now averages 95 mph, up from 91.3 mph last year, and it spins more than 150 revolutions per minute faster, giving it more “rise” than most fastballs.

Montgomery’s trip to the bullpen at age 26 revitalized his fastball, but that makes him an exception: Most pitchers see their stuff decline from year to year. Specifically, pitchers tend to surrender velocity as they age, forcing them to become craftier — or lose their jobs. Take Dallas Keuchel, last year’s American League Cy Young winner, as an example of a pitcher with a deteriorating fastball: He’s lost almost 2 mph off his four-seamer since 2015, along with 290 rpm of rotation.

Keuchel’s ERA is up more than 3 runs this year, and although not all of that can be pinned on his sagging fastball, it’s a concerning drop-off for a pitcher whose stuff wasn’t exactly overpowering in the first place.

Sliders

LARGEST IMPROVEMENTS LARGEST DECLINES PITCHER CHANGE/100 PITCHER CHANGE/100 1 Kendall Graveman -0.54 1 Aaron Sanchez +0.81 2 Vance Worley -0.53 2 Brett Oberholtzer +0.57 3 Robbie Ray -0.38 3 Anibal Sanchez +0.41 4 Noah Syndergaard -0.37 4 Alexi Ogando +0.40 5 Dillon Gee -0.35 5 Carlos Torres +0.34 6 Nathan Eovaldi -0.34 6 Brandon Maurer +0.34 7 Trevor Bauer -0.33 7 Randall Delgado +0.31 8 Jose Alvarez -0.33 8 Justin Verlander +0.26 9 Wily Peralta -0.32 9 Chris Hatcher +0.23 10 Trevor May -0.29 10 Hector Neris +0.22 Biggest changes in sliders from 2015 to 2016, by change in runs per 100 pitches Negative run values are better — the pitcher is allowing fewer runs. Source: Pitchinfo

It doesn’t rank No. 1, but perhaps the most impressive of all slider improvements has come from the Mets’ Noah Syndergaard, given the difficulty of tacking 3.5 mph on to what was already the ninth-hardest slider in the game. Although the man they call Thor has seen his slider slow a bit since his initial April outings — its average velocity has fallen from 93 mph heat to 91 mph — it’s still the fastest in baseball, and the increase has made it borderline unhittable.

Not bad for a pitch he threw only 2 percent of the time a year ago!

Syndergaard gained all of that velocity at the cost of some spin on his slider, giving it slightly less horizontal movement. Even more so than with the fastball, the trade-off between a slider’s speed and spin rate is a delicate balance that can make or break its effectiveness.

Curveballs

LARGEST IMPROVEMENTS LARGEST DECLINES PITCHER CHANGE/100 PITCHER CHANGE/100 1 Jesse Hahn -0.55 1 Jaime Garcia +0.53 2 Mike Wright -0.54 2 Madison Bumgarner +0.36 3 Mike Montgomery -0.54 3 Jordan Lyles +0.34 4 Adam Morgan -0.50 4 Jose Quintana +0.34 5 Randall Delgado -0.44 5 John Lamb +0.31 6 Taijuan Walker -0.35 6 Mat Latos +0.29 7 Robbie Ray -0.34 7 Yordano Ventura +0.26 8 Carlos Villanueva -0.32 8 Chad Bettis +0.26 9 Martin Perez -0.31 9 Johnny Cueto +0.26 10 Andrew Cashner -0.30 10 David Price +0.25 Biggest changes in curveballs from 2015 to 2016, by change in runs per 100 pitches Negative run values are better — the pitcher is allowing fewer runs. Source: Pitchinfo

Montgomery again! He shows up twice on my lists: No. 1 under MLB’s most-improved four-seamers and also among its most-improved curveballs. As was the case with his fastball, Montgomery managed to pick up more than 3 mph on his curve, to go with almost 700 extra rpm; it now breaks just over 50 percent more than it did last season. Those two drastically improved pitches go a long way toward explaining how Montgomery’s ERA has dropped to half of what it was during his lackluster 2015 season.

We tend to frame velocity changes in terms of a pitcher’s fastball, but a slower curveball can cause problems, too. The Kansas City Royals’ Yordano Ventura has maintained his four-seam heat just fine, but he’s lost about 2 mph of velocity (plus some spin) on his curveball. All else being equal, slower pitches — of all types — are less effective because they give the batter more time to react and decide whether to swing. Perhaps for that reason, Ventura’s curve has gone from his best pitch to a far more mediocre offering, just as his ERA and fielding independent pitching have ballooned.

Change-ups

LARGEST IMPROVEMENTS LARGEST DECLINES PITCHER CHANGE/100 PITCHER CHANGE/100 1 Christian Friedrich -0.22 1 Justin Miller +0.19 2 Alfredo Simon -0.21 2 David Price +0.15 3 Colin Rea -0.19 3 Kevin Gausman +0.13 4 Mike Foltynewicz -0.17 4 Colby Lewis +0.13 5 Archie Bradley -0.17 5 Derek Holland +0.12 6 Mike Montgomery -0.12 6 Adam Conley +0.10 7 Cody Anderson -0.11 7 John Lamb +0.10 8 Vance Worley -0.10 8 R.A. Dickey +0.09 9 Kendall Graveman -0.09 9 Madison Bumgarner +0.08 10 Scott Feldman -0.08 10 Shelby Miller +0.08 Biggest changes in change-ups from 2015 to 2016, by change in runs per 100 pitches Negative run values are better — the pitcher is allowing fewer runs. Source: Pitchinfo

Change-ups are generally deployed less frequently than the other pitch types I’ve mentioned, but they can be particularly potent weapons against opposite-handed batters. One pitcher who seems to have discovered this is lefty Padres starter Christian Friedrich, who has traditionally struggled to retire righties. With more reliance on a newfound change-up that spins nearly twice as much as last year’s version, Friedrich has managed to lower his weighted on-base average allowed to right-handers from .409 to .274, and his overall results have improved as well (2.12 ERA, 3.36 FIP).

But then there’s Kendall Graveman, who shows up on three of the lists: He has the most-improved slider, fourth-most-improved fastball and the ninth-most-improved change-up. In theory, Graveman should be using his array of better pitches to overwhelm hitters; instead, he’s sporting a poor 5.28 ERA, an even worse 5.29 FIP and a depressingly sub-replacement-level WAR.

A former prospect, Graveman hasn’t converted his stuff into measurably good results, joining the long list of pitchers whose raw ability doesn’t translate into dominance on the mound.

That’s why every hurler is more than just the sum of his pitches. Individual offerings play off each other in unexpected — and still inexplicable — ways. A pitcher’s stuff can be fantastic, but without command and control, the results will be poor. Factors such as deception and sequencing still resist most sabermetric analysis, and so a significant part of how pitching works remains unknown. In other words, we can measure what makes a pitch great, but it’s much more difficult to figure out what makes a pitcher excel.