As fantasy owners, we love to see significant improvement in a pitcher’s performance. A sudden spike in strikeout rate or drop in ERA can be the signs of a breakout season that could lead to a fantasy championship.

Recently, we looked at changes in pitcher velocities, and how they were positively or negatively impacting performances. Today, let’s look at some pitchers who have changed their pitch arsenals, either by adding a pitch or merely changing how often they throw certain pitches.

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Cole Hamels (SP – TEX)
Hamels probably isn’t destined to be inducted into the Hall of Fame, though he’s had an excellent career. But, as with most pitchers, he’s dealt with a loss of velocity as he’s gotten older. A more than one mile-per-hour drop in his fastball velocity last year led to a bloated 4.20 ERA and an abysmal 6.39 K/9. Entering his age-34 season, he looked done as a fantasy option and went undrafted in some leagues.

Hamels’ velocity has continued its decline this season, as he’s averaged less than 92 miles per hour on his fastball this year, down about half a mile from his already diminished velocity of 2017. And yet his ERA sits at 3.48 (career mark of 3.37), and his strikeout rate is above his career mark (9.93 per nine innings, 8.52 for his career) through mid-May.

The reason? Well, there are two. The first is that Hamels added a slider.

At 34 years old and after more than 2,300 innings pitched in his career, Hamels simply started throwing a pitch that, by all accounts, he had NEVER thrown in a Major League game before. Hamels isn’t relying on his slider in any significant way. He’s throwing it only about five percent of the time. But it’s been incredibly effective (.083 batting average against) and keeps hitters honest.

The second reason is that he’s just throwing his fastball far less. Hamels’ fastball is not good at this stage of his career. Batters are hitting about .390 off it this year. But because he’s throwing it far less (just 35% of the time when he’s been above 45% for his career), the damage has been relatively minimal.

Hamels is what you hope to see out of every aging pitcher. A recognition that his raw stuff can no longer support his old way of doing things, and that a change is necessary to counteract that plain fact. If he keeps it up, he should stave off Father Time for just a little bit longer.

Carlos Martinez (SP – STL)
Martinez is currently on the disabled list with a lat strain, but he has been having an excellent season, at least on the surface. His 1.62 ERA ranks third among qualified starters, and his 1.08 WHIP is by far the lowest of his career. There is plenty to suggest that his numbers were the product of luck – his strikeout rate is down, his walk rate is at a career high, and his FIP and xFIP are significantly higher than his ERA (though they usually are).

Batters are also generally having less success on balls put in play, batting just .179 against him with a .237 BABIP. And, most likely, some of that is due to luck. But another part of it is that Martinez has introduced a cutter for the first time in his career. Martinez has thrown his cutter roughly 16% of the time, and the results have been promising. Batters are hitting just .219 against the pitch with a .281 slugging percentage.

Martinez has made room for his cutter by throwing his four-seam fastball less, reducing his usage of that pitch from 27% to about 14.5%. And the introduction of his cutter has lowered the batting average against his four-seam fastball from .236 to .088.

Regression is going to come for Martinez, but the introduction of his cutter has also helped the effectiveness of his four-seam fastball. That suggests that his increased performance might be somewhat more sustainable than previously thought.

Patrick Corbin (SP – ARI)
Corbin has been one of the best pitchers in baseball over the first six weeks of the season. His 11.84 K/9 rate ranks fifth in baseball, and he’s setting career-bests in every statistical category.

The reason is fairly straightforward. He’s continued the trend that he started in the second half of last year – he’s throwing his slider an absurd amount of the time. Here’s a look at Corbin’s splits from last year:

• First half: 4.71 ERA, 1.53 WHIP, 20.8% strikeout percentage
• Second half: 3.26 ERA, 1.29 WHIP, 22.5% strikeout percentage

Corbin’s dramatic improvement in the second half is due to a few factors but none bigger than this — in the first half of the season, he threw his slider 34.67% of the time. In the second half, he threw the pitch 41.96% of the time.

This year, Corbin is sticking close to his second-half approach, throwing his slider nearly 39% of the time. And it’s only become more effective. Last year, batters hit .184 against the pitch. This year, they’re hitting a minuscule .093! (Note: according to FanGraphs, Corbin has the best slider in the game).

This is not to say Corbin is without risk. He’s seen a drop in velocity lately, and there’s certainly an increase in injury risk when a pitcher throws his slider close to 40% of the time. But so long as he remains healthy, Corbin should remain an extremely valuable starter this season.

Blake Snell (SP – TB)
Finally, let’s briefly touch on Snell. Snell’s ascension this year has been primarily due to his increased velocity (which we discussed last week) and better command. But he’s made a subtle change to his arsenal that has also helped boost his performance.

Snell has always had an excellent curveball. But this year, rather than throwing it his typical 10% of the time, he’s upped it about 15%, reducing his fastball and changeup usage slightly. Therefore, the results have been the product of simple math.

Here are the batting averages against those three pitches last year and this year:

2017

• Fastball: .237
• Changeup: .260
• Curveball: .173

2018

• Fastball: .247
• Changeup: .237
• Curveball: .171

The results against Snell’s pitches aren’t much different between last season and this one. He’s simply throwing his better pitch more than he used to. It’s a simple and common-sense change that, along with Snell’s other improvements, should mean continued success for the youngster.

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Dan Harris is a featured writer for FantasyPros. For more from Dan, check out his archive or follow him on Twitter at @danharris80.