KC Royals: The uncertainty of the new 3-batter rule

Beginning this season, and with limited exceptions, major league pitchers must face at least three batters. How might this new rule affect the KC Royals?

Rob Manfred is a curious commissioner, a cart-before-the-horse kind of chief executive who seems to create solutions, then search for problems with which to pair them. To him, baseball is a game afflicted by a pace of play plague curable only by his mound visit limits and pitch clocks. His latest proposal to save baseball from itself takes effect this season and will, with few exceptions, require pitchers to face at least three batters; designed to speed up the game by cutting down on pitching changes, the rule will increase the uncertainty surrounding the KC Royals’ bullpen.

The new rule isn’t complicated, but its implementation and impact could be. All pitchers must face at least three batters, so pitching changes designed to match lefty against lefty (or righty against righty) and to end with that at-bat only to trigger another switch, will be things of the past. There are exceptions: a new pitcher needn’t face the minimum if he completes the half-inning in which he entered the game, or is injured or becomes ill. These are exceptions, however, that won’t swallow the rule.

Because it is impossible to determine with advance precision the frequency of matchups that might fortuitously end innings, occur with only one out, or involve injury or illness, any attempt to quantify the statistical impact of the new rule is folly. Easier to foretell, however, is its impact on game strategy–planning for “handedness” matchups will now require an “other-handedness” component, as managers changing pitchers to set up a lefty-lefty pairing must account for which side of the plate subsequent batters hit.

Skippers must now pay more heed to how each of their relievers performs against lefties and righties; the left-handed “specialist” role may be permanently limited or disappear completely. For new KC Royals’ manager Mike Matheny, the trick will be to determine which relievers perform the best against all hitters regardless of handedness, a task perhaps easier said than precisely done.  (Matheny doesn’t have to analyze his starters in quite the same way–nothing in Matheny’s managerial past suggests he will use “openers”).

Of course, the maxim that left-handers are toughest on left-handed batters, and righties on righties, doesn’t always hold true. Take, for example, new KC Royals right-handed reliever Trevor Rosenthal, one of a handful of reclamation projects General Manager Dayton Moore signed over the winter and invited to Spring Training, and who definitely defies the general handedness rule. A veteran of seven big league seasons, Rosenthal has faced hitters almost 1,500 times, mostly in short relief, and held righties to a .243 average, but lefties only hit .213 against him.

Greg Holland, the former superb right-handed KC closer who signed with the club to search for his old lock-down form, also defies the rule. Righties have hit only .220 against him in 954 plate appearances, while lefties managed only .191 in 942 PAs.

Presumptive closer and right-hander Ian Kennedy is also traditionally better against lefties (.242) than fellow right-handers (.256). The difference was even more pronounced in 2019, his first season spent exclusively as a reliever–lefties batted 72 points lower against him (.226) than righties (.298).

Another (but less successful) exception to the rule is Glenn Sparkman, a right-hander who split time between the rotation and bullpen the last two seasons–left-handers hit .286 against him in his three big league seasons while righties hit .325.

Left-handers also have less success against right-hander Kyle Zimmer (.286) than righties (.375); the Zimmer sample size is small, however, because it’s based on only 18 major league innings. The same goes for newcomer Chance Adams, a right-hander against whom lefties have hit .297 and righties .364 in 156 plate appearances.

There are, of course, Royals who perform consistently with the handedness theory. Most notably, Tim Hill, one of the few lefties in the Kansas City bullpen, is better against lefties (.211) than righties (.259). Right-hander Scott Barlow, expected to set up Kennedy this season, fares best against righties (.219) but lefties hit him more easily (.281). Lefties also hit better against right-handers Kevin McCarthy and Jorge Lopez (.291, .307) than righties do (.264, .267).

To whom, then, should Matheny turn first when he needs to shut down one batter in a high-leverage, no-out or one-out situation, knowing his selection must pitch to others even if he retires the threat of the moment? Assuming Kennedy is his closer, thus reserved for ninth or extra-inning work, Matheny should limit his choices to relievers who do well against both righties and lefties.

Based on BAA (batting average against) alone, Matheny’s top choices would seem to be Holland, then Rosenthal. Over his career, Holland has held everyone down well: lefties have hit .191 and righties .220, just a 29-point difference; Rosenthal’s differential is nearly the same–29–as lefties hit .213 and righties .243. Their most recent numbers are also good: lefties batted .180 against Holland and .174 against Rosenthal, righties .215 and .233.

Hits, however, aren’t the only way to get on base. Walks are the next best thing and can just as easily lead to runs; therein lies the rub for Rosenthal and Holland. Rosenthal walked 26 in 15 innings last season–an astonishing 15.3 BB9 and a source of his stratospheric 13.50 ERA. Holland’s 2019 walk rate of 6.1 contributed to his 4.54 ERA, an excessive number for a short reliever. Unless these veterans harness their control problems, Matheny will need to look elsewhere for a multi-batter stopper.

But he may do that anyway. Hill’s handedness-based BAAs aren’t quite as good as Holland’s or Rosenthal’s, but his .211 against left-handers and .259 against right-handers render him a viable candidate for high leverage work. His control is far better than either veteran’s; that, combined with his more than serviceable 2019–2-0 with a 3.63 (131 ERA+), 8.8 SO9, 2.9 BB9, .186 BAA (left) and .238 (right)–may well make him Matheny’s top relief choice in tough, non-closing spots.

The field of other potential multi-batter stoppers is dangerously thin; no other KC Royals’ relievers limit hits like Hill, Holland and Rosenthal.  In fact, the high BAAs of too many KC relievers eliminate them from serious consideration for high leverage use and reflect the club’s shallow bullpen depth.

The new three-batter rule will challenge Matheny’s bullpen management, a frequent target of critics when he managed St. Louis. Usually, he won’t be able to use Hill to get just one lefty; instead, he’ll have to be confident Hill can retire successive hitters regardless of handedness. Will the new skipper choose to use certain pitchers only in two-out situations, hoping they get that final out and can be replaced immediately? Will he be willing to buck convention and use righties against lefties, and vice versa, when analytics justifies it?

Baseball’s new three-batter rule probably won’t shorten games significantly, but it will change managers’ thinking and strategy. And it will challenge the KC Royals, a team with a questionable bullpen and few relievers who pitch well against both right-handers and left-handers.