There’s certainly been a lot of buzz around the Toronto Blue Jays 28-year old right hander Marcus Stroman leading up to the 2019 trade deadline. The 5’8 Stroman is best-known for two things: getting a ton of ground balls and his nasty slider.
Since the start of 2014, Stroman has been one of the best in baseball at inducing ground balls. Among pitchers who have thrown at least 750 innings over that span, Stroman ranks second with a 59.7% ground ball rate, behind only Dallas Keuchel (60.1%). Getting batters to hit the ball on the ground suppresses offensive production. According to Statcast, since 2015, hitters have produced a .226 wOBA on all ground balls, compared to .488 wOBA on all other types of batted balls (fly balls, line drives, and pop ups). wOBA, which stands for weighted on-base average, is a statistic that measures total offensive production at the plate using the same scale as on-base percentage. But, unlike OBP, which attributes the same value to all on-base events (walks, singles, home runs, etc.), wOBA attributes the actual average run-producing value of each on-base event for that season to every on-base event a hitter has accumulated (for example, in 2013, the average run value of a walk was 0.690, 0.888 for a single, and 2.101 for a home run). To provide some context, the MLB average wOBA in 2019 is .317.
Back to Stroman: below are his ground ball rates and his MLB rank among pitchers with more than 100 innings pitched in each season (excluding his rank in 2015, when he threw only 27 innings due to an ACL tear).
| Year | IP | GB% | MLB GB% Rank |
| 2014 | 130.2 | 53.8% | 13 |
| 2015 | 27 | 64.1% | N/A |
| 2016 | 204 | 60.1% | 1 |
| 2017 | 201 | 62.1% | 2 |
| 2018 | 102.1 | 62.1% | 1 |
| 2019 | 110.2 | 57.9 | 1 |
Stroman gets so many grounders thanks to his sinker, which is the pitch he’s thrown most often in his career at 42.5% (according to Brooks Baseball). In 2019, Statcast data tells us that Stroman’s sinker gets an average of 27.6 inches of vertical break, good for 15% more downward movement than the average sinker thrown at a similar velocity, ranking the pitch’s downward break 29th out of the 198 sinkers thrown more than 100 times so far in 2019. As a result, Stroman’s sinker has led to average launch angles of at least -5 and ground ball rates of at least 67.6% since 2015. Despite the extremely low launch angles, Stroman has allowed high exit velocities on the pitch, likely because it suffers from much below average horizontal break (24% less than average, ranking it tenth-worst among the 198 sinkers thrown 100 times in 2019).
| Year | Launch Angle | GB% | Exit Velocity | wOBA | xwOBA |
| 2015 | -8 | 75.8% | 88.9 mph | .240 | .256 |
| 2016 | -5 | 67.6% | 91.3 mph | .351 | .337 |
| 2017 | -5 | 73.2% | 89.1 mph | .357 | .368 |
| 2018 | -5 | 70.9% | 91.6 mph | .390 | .379 |
| 2019 | -5 | 69.8% | 89.2 mph | .352 | .342 |
Ground ball rate plus strikeout rate is another statistic some MLB front offices like to consider. Nothing suppresses offense as effectively as strikeouts, so a high number of combined ground balls and strikeouts will typically lead to good outcomes for pitchers. Below are the top ten pitchers since 2014 in ground ball percentage plus strikeout percentage (minimum of 750 innings pitched).
| Player | IP | GB% | K% | GB% + K% |
| Dallas Keuchel | 982.1 | 60.1% | 20.0% | 80.1% |
| Clayton Kershaw | 1015.1 | 49.6% | 29.7% | 79.3% |
| Marcus Stroman | 775.2 | 59.7% | 19.3% | 79.0% |
| Carlos Martinez | 808.2 | 53.2% | 23.4% | 76.6% |
| Carlos Carrasco | 921 | 47.9% | 28.1% | 76.0% |
| Sonny Gray | 934 | 53.5% | 21.4% | 74.9% |
| Jake Arrieta | 1037 | 51.3% | 23.4% | 74.7% |
| Stephen Strasburg | 917.2 | 45.1% | 29.1% | 74.2% |
| Felix Hernandez | 872 | 52.0% | 22.0% | 74.0% |
| Chris Sale | 1093.1 | 41.5% | 32.4% | 73.9% |
The average ERA and FIP of the above group since 2014 are 3.28 and 3.32, respectively. Just missing the top ten is Jacob deGrom, and other notable names in the top twenty include Corey Kluber, Gerrit Cole, Masahiro Tanaka, and Zack Greinke. Stroman’s ERA (3.82) over that span ranks last in this group, and his FIP (3.63) ranks 8th, due to his low strikeout rate, but his inclusion shows precisely why he’s been an effective pitcher since he came up in 2014.
Getting ground balls is even more important at Yankee Stadium, especially for right-handed pitchers. Since 2015, the wOBA against right-handed pitchers in Yankee Stadium on fly balls, line drives, and pop ups is .508, twenty points higher than the league average in that span (potentially due to the short porch in right field). Additionally, thanks to park factors, we know that home runs have historically been easier to come by in Yankee Stadium than in other ballparks throughout baseball. Here’s how ESPN’s MLB Park Factors have ranked Yankee Stadium’s propensity for surrendering home runs since 2014.
| Year | MLB Park Factor Home Run Rank |
| 2014 | 1st |
| 2015 | 4th |
| 2016 | 1st |
| 2017 | 2nd |
| 2018 | 6th |
| 2019 | 21st |
One note on the 2019 ranking, which is pretty jarring. It’s hard to believe that Yankee Stadium could play so differently in 2019 than it has in the past. There is a ton of evidence that the baseballs being used in 2019 are drastically different than those used in any other season, with the alarming home run totals this year being the biggest tip-off. That difference could be one reason Yankee Stadium is seeing fewer home runs compared to other MLB ballparks this season.
The chart above shows that Stroman has followed recent league-wide trends, moving away from his sinker and throwing his excellent slider more often. In 2019, he’s throwing his sinker a career-low 35.9% of the time, and he’s throwing his slider at a career-high 34.2% clip. The results against his slider speak for themselves (for context, the league-wide wOBA on sliders since 2015 is .267; Whiff% is the percentage of swings-and-misses a pitcher gets on all swings).
| Year | Usage | Exit Velocity | wOBA | xwOBA | Whiff% |
| 2015 | 17.7% | 94.2 mph | .292 | .355 | 25.0% |
| 2016 | 13.1% | 92.1 mph | .251 | .257 | 31.3% |
| 2017 | 24.4% | 86.7 mph | .216 | .216 | 40.7% |
| 2018 | 30.4% | 87.5 mph | .255 | .247 | 32.6% |
| 2019 | 34.2 | 86.1 mph | .192 | .229 | 36.3% |
According to Statcast, Stroman’s slider averages 11.3 inches of horizontal break, 99% more than average sliders thrown at a similar velocity. Stroman’s horizontal slider break ranks 22nd of the 248 pitchers who have thrown over 100 sliders in 2019. His slider also gets above-average drop: 4% higher than average, which his good for top 30% within the same group. Here’s Stroman’s slider in action (credit to MLB.com’s Baseball Savants site for the video).
In their seminal 2019 book The MVP Machine, Ben Lindbergh and Travis Sawchik detailed how the Cleveland Indians’ Trevor Bauer specifically studied Stroman’s slider while developing his own early in the 2018 season. Using a high-speed Edgertronic camera to record Stroman in a start he made against Cleveland, Bauer dissected slow motion video of Stroman throwing his slider, paying particular attention to how the pitch came out of Stroman’s hand as he released it. Teams on the forefront of the player development movement have certainly begun to use Edgertronic cameras in this way to gather intelligence about the best ways to release certain pitches to get the desired movement on each pitch. A team can always gather more intelligence when a player is in its own system.
The Yankees’ love of sliders is well-documented. No team has thrown more sliders than the Yankees in 2019 (21.3%), and they’re tied with the Rangers for the highest slider usage since 2017 (18.4%). Given their infatuation with sliders, you can bet the Yankees would benefit from learning more about how Stroman throws the pitch and using that information to teach pitchers throughout their system, both at the major and minor league level, the best way to throw sliders. In 2019, that intel could be just the thing that moves the needle for the Yankees (or another team) in a deal for Stroman.
Despite his increased slider usage, Stroman remains below average in strikeout rate in 2019 (19.1% where league average is 22.7%) as a result of his high-sinker usage. There are some interesting things about Stroman’s profile, however, that suggest he has greater swing-and-miss potential.
Stroman’s average four-seam fastball spin rate sits at 2,488 revolutions per minute (RPM) in 2019, just behind Aroldis Chapman and Max Scherzer and just ahead of Clayton Kershaw and Rich Hill. That spin rate ranks Stroman’s four-seamer 36th out of 502 four-seam fastballs thrown at least 50 times in 2019 (in the top 7th percentile). High spin rates on four-seam fastballs typically lead to high swing-and-miss rates. High-spin four-seamers have the potential to combat the force of gravity, causing the baseball to drop less on its path to the plate. That less-than-average drop generates swings under the baseball, resulting in more swings-and-misses, pop ups, and fly balls. Although Stroman’s four-seamer has a high spin rate, he gets below average “rise” (the term used to describe the less-than-average drop) on the pitch: 14% below average, ranking it 433rd of 502 four-seamers thrown 50 times or more. In contrast, Rich Hill, who has a slightly lower four-seam spin rate than Stroman, gets 10% above average rise.
Spin rate alone doesn’t create the rising effect perceived by hitters; spin efficiency is also required. Spin efficiency can be explained pretty simply: a pitch may be spinning very quickly, but if it’s spinning on the wrong axis, it won’t create the desired movement. Spin efficiency can be corrected with the use of Edgertronic cameras to alter a pitcher’s pitch grip, release, or release point (or all three) until a pitcher is getting the desired movement on a particular pitch. Its high spin rate and below-average rise indicates that Stroman’s four-seam fastball suffers from poor spin efficiency, making it ripe for development into an effective weapon. A team willing to work with Stroman to improve the spin efficiency on his four-seamer (a pitch he’s only using 3.6% of the time in 2019) could extract hidden value from the Blue Jays starter by creating a pitch with higher swing-and-miss rates to replace some of his less effective pitches.
A deal for Stroman would bring back an effective pitcher who keeps the ball on the ground and in the ballpark, is on the right side of 30, and has no history of serious arm trouble, a rarity in 2019. Other than his ACL tear in 2016, Stroman has only missed time for right shoulder inflammation and fatigue as well as blisters on his pitching hand. Stroman doesn’t enter free agency until after the 2020 season, giving teams an extra year of control. That extra year of control means Stroman will command a higher price than a true deadline rental. For the Yankees, that turns what was already a negative into an even larger one, as they’d be trading prospects to a division rival whose farm system has consistently been ranked in the top ten in baseball in 2019 (5th by MLB.com, 8th by FanGraphs, 9th by ESPN’s Keith Law). However, that extra year of control also gives teams an extra year to mine Stroman for information on how he throws his slider and more time to tinker with Stroman’s four-seam fastball and potentially squeeze even more value out of what is already a very good major league pitcher beyond the 2019 season.
Back To The Bronx 
Really interesting. Great read.
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