Overthinking It: When Big Leaguers Go Back to the Bush Leagues

The first inspiration for this article was watching the Futures Game. We know that the Futures Game is great because it gives us a chance to see top prospects face off against top prospects. But an underrated aspect of its appeal is that it sometimes pits top prospects against much less advanced top prospects, letting us see, say, 19-year-old Dilson Herrera, who’s in A-ball, hit against 23-year-old C.J. Riefenhauser, who’s in Triple-A (Herrera flied out). Riefenhauser may not have a super high ceiling, but he’s by far the most mature pitcher Herrera has ever had to hit against. The four years and three levels of development between those two players makes a massive difference—much more than the months and the lone level that separate the Futures Game rosters’ more advanced members from the majors. (Actually, World Team member Henry Urrutia has already been called up by Baltimore.)

The second inspiration for this article was podcast questions. A few weeks ago, a Fringe Average fan asked what Miguel Cabrera would hit in the minors. Effectively Wild listeners often ask the same sort of thing. (“What would my ERA be in the majors?” wondered one formerly league-average little leaguer.) Judging by my own curiosity and the kind of questions we get, we’re all intrigued by showdowns between players of dramatically different ability.

Fortunately, there is one way to see such lopsided matchups, which takes us to the third inspiration for this article: the results of some currently or recently rehabbing players. Derek Jeter going 1-for-9 with a single and four walks for Triple-A Scranton. Alex Rodriguez hitting .188/.250/.406 in a combined 36 A, High-A, Double-A, and Triple-A plate appearances. Colby Lewis getting knocked around to the tune of a 9.82 ERA in four short Double-A and Triple-A starts.

We don’t know what Miguel Cabrera would hit in the minors, because he hasn’t played there since 2003 and has no incentive to do so. But many major leaguers do return to the minors to rehab against a level of competition they’ve long since left behind. How do rehabbing big leaguers fare against hitters who can barely touch a breaking ball and pitchers who hardly have one? Thanks to Corey Dawkins’ 2005-12 DL data, which includes the dates that players joined and left the big-league disabled list, we can query for rehab results and find out.

***

Disabled major leaguers most often rehab at Triple-A, followed by (in descending order) High-A, Double-A, rookie ball, full-season A ball, and short-season A ball. For reference, here are the 2005-12 run environments at each level:

Double-A offers conditions closest to the majors, while Triple-A (Pacific Coast League) and High-A (Cal League) are better hitting environments. The lower in level you go, the worse the fielders (and fielding conditions) get, and the bigger the gap between runs per nine and ERA.

Pitchers
The first six columns show the collective major-league stats produced—in the same season as the rehab assignment—by the group of pitchers who rehabbed at a given level. The six columns to the right of those show stats produced in those pitchers’ rehab assignments. The second row reveals that pitchers who rehabbed at Triple-A from 2005-12 posted a combined 4.04 ERA while rehabbing; those same pitchers recorded a 4.68 ERA in the majors in the same seasons as their rehab assignments. The two rightmost columns shows the percentage decrease in ERA from MLB to each lower level, and the same percentage decrease adjusted for the minor-league level’s run environment.

So as we would expect, big leaguers allow fewer home runs, walks, and strikeouts when rehabbing at Triple-A than they do in the majors. Their rehab ERAs are roughly 14 percent lower, or 17 percent lower if you adjust for the fact that more runs are scored in Triple-A. There’s a fairly smooth trend toward better performance the lower in level they go, with the only blip being short-season A, which has by far the smallest sample (under 90 innings). Rehabbing big leaguers post ERAs roughly half as high in rookie ball, as subpar opponents turn below-average big-league arms into aces.

Batters

Rehabbing batters don’t seem to get as big a boost as pitchers. It’s hard to say why. Maybe it's because batters are at a bigger disadvantage when they’re facing unfamiliar opponents; maybe it's because they’re more affected by inferior conditions at lower-level fields. Plus, pitchers and hitters have slightly different rehab goals. Pitchers rehab to build up their arm strength and stamina, but they might be almost as effective as when healthy on a per-pitch basis. Hitters rehab to regain their timing, so taking a few games to adjust their swings is pretty much the point. And rehabbing pitchers are often starters whose stuff might play up in abbreviated minor-league outings.

Obviously, these performance changes don’t show the true talent gap between major and minor leaguers. Disabled major leaguers on rehab assignments are at best rusty from the time they’ve spent on the shelf, and at worst not completely recovered from whatever injury (or injuries) they’ve sustained. Hitters might not run hard; pitchers might not use their full complement of pitches. What’s more, they might not be motivated, even aside from any lingering physical concerns. Rehabbing players want to make it back to the majors, but they don’t necessarily need to dominate to get the call; they just need to show that they’re healthy. And having been exposed to the bright lights and big cities of the big leagues, they may have a hard time psyching themselves up for meaningless games against lower-level opponents. As the rehabbing A-Rod said recently, “I wish I was a little more nervous.”

David Ortiz, another star who struggled in a recent rehab assignment, hit .222/.222/.389 in six April games for Triple-A Pawtucket, striking out in a third of his at-bats. As Gabe Kapler wrote in his treatise on why baseball players shouldn’t fear fear,

By all accounts he looked awful. Onlookers who saw him swing at everything wondered if he was ready for Major League at-bats. Boom, he immediately began raking upon his return to Boston…

Ortiz has hit .317/.402/.606 for the Sox this season. Maybe his slow start in Pawtucket was just a small sample, or maybe his mind was elsewhere.

There’s another potential confound here. The more seriously injured and/or ineffective a player is, the more time he’ll spend rehabbing, and the less time he’ll have when he gets back to the majors (if he makes it at all). As a result, players who struggle on their rehab assignments might be overrepresented in the minor-league samples, skewing the stats somewhat.

As the Jeter, Rodriguez, and Lewis lines attest, rehabbing major leaguers don’t dominate their bush-league brethren to the extent one might expect. But that’s not because they don’t have the skills to make minor leaguers look silly; it’s because they’re playing with an arm, a leg, or a brain tied behind their back. So what would a healthy, motivated Miguel Cabrera hit in the International League? We’d probably have a better shot at answering that question if we looked at how minor leaguers played after being promoted. Because after looking at big leaguers heading in the other direction, we still can’t say.

Thanks to Ryan Lind, Rob McQuown, and Colin Wyers for research assistance.