Astros Trade Hypothetical: Three relievers to target in a trade this summer

Reliever Number Two: Kelvin Herrera

While Herrera doesn’t fulfill the Astros’ perceived need of another quality left-handed in the bullpen, the Royals’ closer would be an upgrade in the later innings based on his season to date.

2018 statistics

25.2 IP, 23.2% strikeout rate, 2.1% walk rate, 1.05 ERA, 2.63 FIP, 3.51 xFIP, 0.7 fWAR

Herrrea has rebounded from a rough 2017 campaign when he posted a 4.25 ERA and 4.30 FIP in 59.1 innings. In fact, he has already been worth more in terms of fWAR — 0.7 — this season than he was last year — 0.1.

There is much to like about Herrera. He strikes out a fair share of batters and his walk rate has been remarkably low. Those are usually two signs of a quality pitcher. Out of all qualified relievers, his 2.1% walk rate is currently tied for the third-lowest in baseball. The pitcher Herrera is tied with is Ken Giles of the Astros. Oh, the irony.

However, Herrera’s numbers this season have been bolstered by a low batting average of balls in play, otherwise known as BABIP. For his career, Herrera has a .282 BABIP. In 2018, Herrera’s BABIP is .246. BABIP for pitchers is known for being to difficult to trust in terms of predicative power on a season-by-season basis. Here is Herrera’s past BABIP measurements since the 2012 season.

• 2012: .313
• 2013: .281
• 2014: .274
• 2015: .249
• 2016: .290
• 2017: .295

Historically, Herrera has only had one season — in 2015 — in which he has posted a BABIP lower than .274 for a season. That said, the Royals’ reliever may keep a low BABIP all season long. But like his 98.9% left on-base rate, I am not sure how long it would last.

To his credit though, Herrera has done an excellent job in limiting home runs. In fact, his home run-to-fly ball rate has dropped by 7.8% compared to last season. His current 6.7% home run-to-fly ball rate is still 3.0% less than his career-average of 9.7%. If he continues to limit the walks and keeps the ball in the ballpark, two things pitchers can usually control, then Herrera has to be a name to watch.

Unlike Hand, Herrera will also be a free-agent at the end of the season. Barring an unexpected development, it should be expected that Herrera finishes the season in a uniform that doesn’t have “Royals” or “Kansas City” embroidered on the front. In theory, Herrera’s impending free agency would keep the price down in terms of prospect compensation. The Aroldis Chapman trade a two years ago may be a favorite comparison point, but I wouldn’t expect a return like the one that the Yankees received from the Cubs. Of course, all it takes is one desperate team.