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The Book of Luke

June 13, 2021
Hugh Atkins

One of the most frustrating things for me to watch in baseball these days is the constant parade of relief pitchers coming into the game from the bullpen. The Atlanta Braves, like most other teams, carry 14 pitchers on their roster. Five of those are starters, so that means they employ nine relief pitchers. Maybe the fact that 35% of the roster is made up of relievers wouldn’t bother me so much if they all were reasonably effective.

While watching the Braves this week, it appeared to me that certain pitchers seem to allow a high percentage of the runners they put on base to score. I’ll pick on A.J. Minter for instance. He has a really good fastball and can be very tough to hit. But I swear it seems as if every batter who reaches base against him eventually scores; I get the same feeling about Tyler Matzek and Will Smith. I realize this suspicion of mine is related to a stretch of close games that did not go the Braves’ way.


I mentioned this suspicion of mine to my son, Sean, at lunch on Friday. I also told him that it seemed to me that Luke Jackson was the only pitcher in the Braves’ bullpen who didn’t get the jitters and allow most of the batters who reach base against him to score. As if to prove my point, that night against the Miami Marlins, Jackson entered the game in the bottom of the seventh inning and promptly gave up a leadoff double to Jesús Aguilar. Jackson seemed unfazed.

The next batter, Corey Dickerson, grounded out to short, and Aguilar moved to third. But Adam Duvall struck out, and Isan Díaz grounded to short. When the dust settled, the inning was over with Aguilar stranded at third. By the way, Jackson threw 10 pitches in the inning, nine of which were strikes.

After Jackson’s performance, I was in Bill Maher territory; “I don’t know it for a fact; I just know it’s true.” I wanted to see if there was any way for me to confirm my suspicions, so I went to Baseball Reference to see what statistics might be available that could at least allow me to test my hypothesis.

I exported the Standard Pitching statistics for the National League into Excel and began to slice and dice the data. I created a stat called Baserunners Scored Percentage (BS%). For the number of baserunners allowed by a pitcher I added the total of his hits, walks, intentional walks, and batters hit by a pitch. This doesn’t take into account runners who reached on a fielder’s choice (in most cases this should be a wash), nor does it count runners who reached via error; I would have liked to include those as well, but I couldn’t find that stat. I then divided the total of runs scored (both earned and unearned) against the pitcher by the number of baserunners he allowed. Finally, I sorted my data by this new stat from smallest to largest.

Lo and behold, going into today’s action, Jackson, at .107, had the fourth lowest BS% among relievers in the NL who have appeared in at least 15 games. Only Dan Winkler of the Chicago Cubs (.067), Alex Reyes of the St. Louis Cardinals (.091), and Josh Hader of the Milwaukee Brewers (.105) have allowed a lower percentage of their baserunners to score.

I’m sure many a Sabermetrician could poke holes in my theory and the data I used to test it. But for now, I’m standing by my assessment of Luke Jackson.

Top 10 NL BS%                
Pitcher Team G R H BB IBB HBP BS%
Dan Winkler CHC 25 2 13 13 0 4 .067
Alex Reyes STL 29 4 15 28 1 0 .091
Josh Hader MIL 26 2 11 8 0 0 .105
Luke Jackson ATL 26 3 16 11 1 0 .107
Mark Melancon SDP 26 4 17 11 2 0 .133
Caleb Baragar SFG 22 4 14 11 2 2 .138
Anthony Bender MIA 16 2 7 5 0 1 .154
Jeurys Familia NYM 21 5 19 11 0 0 .167
Tejay Antone CIN 20 5 12 11 0 3 .192
Andrew Chafin CHC 30 6 17 9 1 2 .207

(All statistics are from Baseball Reference.)


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