Prospect Watch: John Brontsema

John Brontsema was drafted by Kansas City in the 26th round last year out of UC Irvine. A toolsy infielder that can play multiple positions, Brontsema hit the ground running in 2016, slashing .343/.395/.406/.801 over 175 at bats in his first professional season in the Arizona Summer League.

Brontsema performed so well in the AZL that he was actually promoted to High-A Wilmington to help fill in at the end of the season, where he got three hits in three games.

The promotion appeared to be a sign of confidence from the Royals front office. Brontsema didn’t hit for much power in the Arizona League (only 10 XBH, 0 HR), but it’s hard to ignore a guy who gets on base at a .395 clip.

Perhaps in an effort to help him learn to develop some power, Brontsema was assigned to Extended Spring Training to begin 2017. He was originally expected to report to the rookie league Idaho Falls Chukars in June, but was instead sent to fill in with the Low-A Lexington Legends when second basemen Gabriel Cancel had to miss some time with an injury.

Brontsema made the most of his opportunity with Lexington, slashing .345/.424/.517/.941 with his first career home run across 10 games. The impressive start made it nearly impossible for the Royals to send him back to rookie ball, so Brontsema got to stay in A-ball for the remainder of 2017.

He didn’t waste that opportunity either. Brontsema wound up hitting .323 with 4 HR in 52 games with the legends, and even wound up getting a promotion to High-A in the month of August. Brontsema struggled a bit in his time with the Wilmington Blue Rocks, but it was encouraging to see the young second basemen begin to get some attention from the Royals front office.

There are a few interesting peripheral numbers to consider when looking at Brontsema, some good and some bad.

The Good:

Royals Farm Report founder Patrick Brennan is our lead man in the “sabermetric” research category. He does some great work using advanced metrics to gauge prospects and even creating his own metrics in order to compare prospects across different levels of minor league baseball. Read this article to better understand why.

“wOBA” is a statistic that is used to try to get a more accurate depiction of a hitter’s true offensive value. “Weighted On Base Average” is a, “…rate statistic which attempts to credit a hitter for the value of each outcome rather than treating all hits or times on base equally,” according to FanGraphs. In other words, an attempt to combine slugging percentage and on base percentage into one statistic without just adding them together.

Patrick attempted to take FanGraphs’ wOBA and make it more comparable across different minor league levels. For example, the Pioneer League (rookie) is one of the most hitter friendly league in the minors, so you would expect a bunch of higher wOBA’s. Patrick’s goal was to remove league outliers in order to make hitters in the Texas League comparable with those in the Pioneer League. Here is the leaderboard for Patrick’s wOBA z-score:

That’s a pretty impressive list, and Brontsema comes out as having the 17th best wOBA z-score of 3,000 minor league hitters. Second basemen that can hit the ball well are always a commodity, and the Royals appear to have a whole organization full of them (Merrifield, Lopez, Cancel, etc.).

Brontsema walks just enough, with a respectable 8.9% walk rate with Lexington in 2017, and registered a ridiculous wRC+ (another advanced metric used to attempt to get a fairer gauge of a hitter’s true production) of 162. For reference, Eric Hosmer’s wRC+ this year in KC was only 135. That’s pretty impressive for Brontsema, who only hit 4 HR on his way to that 162 wRC+.

The Bad:

Now comes the worrisome part for Brontsema.

Brontsema strikes out a lot for a guy who doesn’t hit with a ton of power yet. Standing at 6′ 2″ and only weighing 187 pounds, there may be time for Brontsema to fill out and develop a bit of power, but it isn’t there yet. After striking out at a rate of 15.4% in the AZL in 2016, Brontsema’s strikeout rate jumped up to 21.6% in 2017 with Lexington. Brontsema actually struck out more times in 2017 (Low-A only) than in 2016 (AZL only) in fewer at bats.

Now, the good part about that is that is SLG% did increase quite a bit, which is always good if you’re going to be striking out more, but Brontsema still strikes out way too much for a guy who doesn’t project to be much of a power hitter.

Brontsema also appears to have been propped up by an outrageous .407 BABIP with Lexington in 2017. A .407 BABIP is incredibly difficult to sustain over a significant period of time. The good news for Brontsema is that if he can manage to get his strikeout rate down, than his batting average shouldn’t take too much of a hit if and when his BABIP regresses to the mean.

Another stat that doesn’t project well for Brontsema if he doesn’t make an adjustment is his line drive/fly ball percentage. Brontsema hit the ball on the ground in 45.5% of his at bats with Lexington in 2017. For reference, Gabriel Cancel’s GB% was only 40.6% in 2017. Look at Whit Merrifield, for example. Merrifield enjoyed a career year in 2017, hitting 19 HRs and slugging .460 in the big leagues. He also cut down on his GB% by 7% since 2016 to get it down to 37.7%.

The days of “hit the ball on the ground” are fading out of the MLB. Unless you have Raul Mondesi or Jarrod Dyson speed, hitting the ball on the ground results in an out far more often than not. John Brontsema could use an adjustment in his swing from the “fly ball era” to help him get his GB% down and his HR numbers up.


Brontsema is an interesting prospect. There are some pieces of his game that are really encouraging and there are also some glaring holes. I’m a big fan of second basemen who can hit the ball well, and Brontsema fits that description, but he’s gonna have to improve on some aspects of his offense in order to make it as a prospect. Brontsema made 14 errors at 3B in 2016 and was moved to 2B for most of the 2017 campaign where the errors were cut to 3, so hopefully the move will help out Brontsema defensively. No matter where he plays though, Brontsema is going to have a tough road ahead of him with the likes of Nicky Lopez, Gabriel Cancel, Emmanuel Rivera, Hunter Dozier, and Whit Merrifield manning second and third base at the upper levels for the foreseeable future. An increase in power production may be Brontsema’s best shot at the big leagues.

Photo Credits: Keith Elkins



One thought on “Prospect Watch: John Brontsema

  1. Pingback: Royals Farm Report Prospect Watch Index | Royals Farm Report

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