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HR/FB% Studs and Duds for Week 8

Welcome back to RotoBaller’s pitchers advanced stats and StatCast studs and duds article series! Each week we will select an advanced stat, choose two studs and two duds, and analyze what those stats could mean for future fantasy output. The next stat we will use is one that is not entirely predictive on its surface but can shed insights into certain aspects of a pitcher’s game, home run to fly ball ratio (HR/FB%).

HR/FB% is fairly straightforward to calculate, as it is the ratio of how many home runs a pitcher allows for every fly ball he allows. Whether or not a ball leaves the park is not entirely under the pitcher’s control given the dimensions of each ballpark, the weather conditions, etc. However, pitchers can work to limit the number of fly balls they allow, so this stat is not purely luck-based.

The rough average for HR/FB% is between eight and 12%, so when a pitcher allows a value significantly outside of that range it could either be due to luck, underlying metrics/performance, or a combination of both. Identifying what lurks under that stat can help fantasy players find buy-low and sell-high candidates. Now that we know the relative value of HR/FB%, let’s take a look at some studs and duds!

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Starting Pitcher HR/FB% Studs 

All stats current as of 5/20/19, courtesy of 


Joe Musgrove - Pittsburgh Pirates

HR/FB%: 3.8%, FB%: 33.8%

Our first HR/FB% stud has been a surprise success this season, posting a 3.67 ERA, 1.07 WHIP, and a minuscule 3.8% HR/FB%. Joe Musgrove was a sneaky late-round pick this season but is currently just 60% owned; should fantasy players go out and try to get him while it's still early in the season? 

Musgrove doesn't have overpowering stuff (fastball velocity of 91.7 MPH) but he has above-average spin on his pitches, which gives him added deception. Further, he relies on strong control (7.7% walk rate) to keep himself out of trouble. That being said, there isn't much more to Musgrove's game that suggests he is a high-end fantasy option. Let's take a further look.

First, despite, the low HR/FB%, Musgrove's batted-ball profile isn't great. His 11.6-degree launch angle, 89-MPH exit velocity, and 38.5% hard-hit rate could easily have resulted in more than just two HR. Further, his 4.46 SIERA also suggests that Musgrove has been overperforming his skills.

Musgrove has performed well to this point and fantasy owners probably took him late in the draft, so he has been a fantasy success in that regard. However, it appears that he has outperformed his underlying metrics, so negative regression can be expected. Those who took Musgrove in drafts can certainly hang onto him, as he is a fine back-end starter. However, he could also be a sell-high target if those owners could flip him for better talent.

Trevor Williams - Pittsburgh Pirates

HR/FB%: 7%, FB%: 35%

Our second HR/FB% stud is a teammate of Joe Musgrove and shares a lot of similarities to him as well. Trevor Williams is putting together his second strong season in a row, posting a 3.33 ERA, 1.13 WHIP, and a mere 7% HR/FB%. Unfortunately, the 27-year-old landed on the 10-day IL after Thursday's start with a side injury. Injury stashes are always important to be on the lookout for, especially early in the seasons and given Williams' numbers it is worth taking a further look at him. 

To this point, Williams' 2019 numbers are very similar to his 2018 numbers. The catch is that this may not be a great sign. Williams doesn't have great velocity and has low spin rates on his pitches, yet he has been successful. He relies heavily on his fastball (56.5% usage) yet has avoided hard contact (85.8 MPH exit velocity, 34.1% hard-hit rate). Further, his 35% FB% isn't great, yet he has managed to avoid giving up HR. Williams' 4.33 SIERA is a whole run different from his 3.33 ERA, indicating that he has significantly overperformed his skills.

Williams outperformed his skills last season and is doing the same thing this season. There are no clear explanations as to why he has been so successful, and it seems as though fantasy players aren't buying into him like they are Musgrove (Williams is just 37% owned, although part of this could be due to his injury). While his underlying stats don't support his performance, there is no reason not to pick Williams up as a streamer against favorable matchups when healthy. The fact of the matter is, he is fantasy valuable until his underlying stats catch up with him if they do. He is worth an IL spot or a bench stash in deeper leagues and should be monitored closely over the next week for updates on his health.


Starting Pitcher HR/FB% Duds 

All stats current as of 5/20/19, courtesy of


Aaron Nola - Philadelphia Phillies

HR/FB%: 20.9%, FB%: 29.3%

Our first HR/FB% dud was a highly touted fantasy option coming into the season but has not delivered on expectations. Aaron Nola has posted a lackluster 4.47 ERA, a 1.55 WHIP, and a massive 20.9% HR/FB ratio in 52 1/3 IP this season. The long balls have clearly hurt Nola to this point; should fantasy owners be worried that they wasted an early pick on him?

Several things stand out regarding Nola’s HR/FB%. We’ll start with the good. While he has given up a large number of HR relative to FB, Nola actually has not allowed all that many FB; his 29.3% FB% is on the lower end amongst starters. Further, his career HR/FB% mark sits at 13.1%, so it seems reasonable to think that his current mark is partly due to bad luck and will regress over time. Finally, Nola has performed much closer to his expectations in May, going 2-0 with a 2.61 ERA and a mere 13.3% HR/FB ratio, pretty much at his career average.

Let’s turn our attention to the bad now. Nola’s command has been off all season long (1.55 WHIP, 1.50 in May) and it has hurt him both in terms of runs allowed and batted-ball profile. His launch angle of 10.1 degrees is respectable, but his average exit velocity of 89.9 MPH and hard-hit rate of 42.3% do not bode well for him in terms of allowing big hits. While he may not allow a ton of FB, he is more likely to allow HR when he does because hitters are hitting the ball harder. The damage of those HR are compounded by the fact that Nola is allowing more baserunners.

Overall, Nola’s high HR/FB% seems a little fluky, but the underlying issues are not encouraging. Even when he has pitched well, his ceiling has been limited by his lack of command. I do not expect Nola’s HR/FB% to remain this high all season long but feel that his overall performance will continue to suffer unless he can start hitting his spots.


Jon Gray - Colorado Rockies

HR/FB%: 24.4%, FB%: 29.9%

Our second HR/FB% dud is one who is certainly at a disadvantage given his home park is Coors Field. However, Jon Gray has posted the highest HR/FB% of his career this season, with nearly a quarter of his FB going for HR. His 4.73 ERA and 1.37 WHIP also leave much to be desired. There has always been hope that Gray would become a fantasy staple, but it has never materialized. Is there any reason to buy into him now?

Two concerning facets of Gray's game stand out regarding his high HR/FB%. The first is the nature of his fastball. Gray has good velocity on the pitch (95.5 MPH) but he gets very little spin on the pitch (1,992 revolutions per minute), making it less deceptive. The harder and straighter a pitch comes in, the harder it goes out, which has what happened this season. Gray has yielded an average exit velocity of 94.5 MPH with the pitch and 40% of his HR.

The second is that, despite pitching his home games in hitter-friendly Coors Field, Gray has allowed most of his HR on the road. Gray has allowed seven HR in six road starts and three HR in three home starts. If Gray cannot keep the ball in the yard during his away starts then his fantasy value will be quite limited.

Gray's career HR/FB% is 14.9%, much lower than his current 24.4% mark, which is the only positive that can be taken from his current situation. His fastball has been getting hit hard and he has been allowing long balls on the road as well as at home. I would try to sell Gray if he can put forth a few solid starts because his underlying troubles are not worth the potential of him panning out.

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