2021 Royals Season in Review - Jake Brentz

First Half

Jake Brentz was a surprise breakout player after a very nice Spring Training in 2021. He was taken in Round 11 of the 2013 draft and spent the next six years toiling in the minor leagues for three different clubs before the Pirates cut him and the Royals took a chance on him. Throughout his minor league career, he was known as a guy who could get lots of strikeouts but could not avoid the walks. None of that changed in 2021 but he did start striking out enough and walking few enough that it made sense to give him a shot in a merit-based Kansas City bullpen with no proven stars and few veterans who weren’t well over the hill.

He started the year doing exactly what the Royals expected and hoped; he struck out a ton, walked a bunch, and did enough to be quite valuable. Even though he was walking guys it was hard for his opponents to get hits off of him. During the first three months of the season, he allowed only 20 hits in 36.2 innings. When you’re striking out more than a quarter of the batters you face and giving up only one hit per about two innings you can get away with a few walks. He quickly entered Mike Matheny’s circle of trust and graduated from left-handed specialist to general-use setup man.

Second Half

Things got a bit dicey for Brentz in the second half. I was prepared to assume he started walking more guys again. Instead, it turns out that he walked fewer and struck out more guys from July-October than he did from March-June. So what happened?

In a word, hits.

After his stellar start, he allowed 25 hits in the final 27.1 innings he pitched, including 11 extra-base hits. Especially bloated was his HR/FB ratio which spiked up over 20% in both July and September. He didn’t allow a single dinger in August, but he allowed plenty of damage in those two months to make up for it. Four home runs may not sound like a lot, but when you’re still walking your fair share and you only pitch 27.1 innings, they can add up in a hurry.

In the end, the damage was done to the point that though he started the season as an excellent reliever who justifiably earned late-inning duty, he finished the season as a replacement-level player.

Future

Jake’s hot start has probably earned him the inside track to a bullpen spot in 2022, and that’s entirely reasonable. Until we see him pitch next year it’s hard to say what happened that led to his decline in 2021. It could have been overuse by Mike Matheny early in the year as was alleged by some. It could be that the league figured out a tell that he might be able to correct over the off-season. He might have just been put into poor positions by the injuries and ineffectiveness of the players around him. He will still only be 27 next year and in the worst-case scenario the Royals could still use him as a medium-leverage lefty specialist.

I specifically mention medium-leverage because in looking at the splits, it turns out that Brentz was pretty awful in high-leverage situations all year. His strikeout rate plummeted, his home run rate skyrocketed, and despite a BABIP and batting average against of both under .200 he still managed to accrue a -9.8% LOB% - he allowed more runs than he did hits, walks, and HBP. It’s a tiny sample size of 44 batters out of the nearly 300 he faced all year, but it’s still something to keep an eye on going forward.

Conclusion

Had Brentz duplicated his first half in the second half of the season it would have been easy to award him with an A. He didn’t, though. Still, he was better than anyone had any right to expect after never being a prospect worth mentioning. There’s also definitely value in even a replacement-level reliever who flashes above-average at times. For that reason, I award him a B for his gallant effort. Here’s hoping he’s able to figure out how to get the hits back down without letting the walks go back up.