On Monday, I aimed to identify the ideal candidate for the five-man infield, inspired by the radical defensive alignment implemented by Ben Lindbergh and Sam Miller of the Sonoma Stompers in their new book, The Only Rule Is It Has to Work. I’ve since finished reading the book, and discovered Lindbergh and Miller also deployed the five-man infield’s cousin: the four-man outfield. A follow-up only makes sense.



The Stompers play a four-man outfield against the Pacifics’ Jake Taylor in San Rafael. (Source)

The boxes to check for our five-man infield were this: lots of ground balls, lots of ground ball hits, ground balls sprayed all over the infield, fly balls with predictable tendencies (either extreme pull or extreme oppo).

For our four-man outfield, it’s essentially the inverse. We want all of the following to be true of our batter:

He hits a bunch of air balls He sprays those air balls all over the outfield He has very predictable ground-ball tendencies

I didn’t use OPS on fly balls as a box to check because OPS on fly balls includes homers, and those can’t be defended against anyway. Remove homers, and the sample gets real noisy, and to me, it didn’t help us in our search. The hitters we’ve identified ended up being good hitters anyway.

So, the hitter that appeared at the very top of our five-man infield spreadsheet was Howie Kendrick, and he checked every box. Made plenty of sense. He was the only hitter to check every box, and I was a bit surprised there weren’t more. Spoiler alert: I’m not totally convinced by any of our four-man outfield candidates. At least not as convinced as I was about Kendrick. But it’s grounds for some interesting discussion nonetheless!

The very top hitter on our four-man outfield spreadsheet? Nick Castellanos. The spray chart:

Castellanos is an extreme air-ball hitter (70%, top-10), and when he hits grounders, he almost always pulls them (77%, top-five). However, while he sprays his air balls, there’s still an interesting distribution. The line drives are almost always pulled, and shallow. The pure fly balls often go the opposite way, and more deep. For this reason, I don’t think the type of four-man outfield the Stompers used (left, left-center, right-center, right) makes sense in this particular scenario; it seems like using a “rover” type positioning in shallow left field to cut down those line drives would be more advantageous. And, really, this isn’t much different than the way teams overshift left-handed batters with the second baseman in shallow right field.

The problem here is that teams already overshift Castellanos with three defenders in the dirt on the left side of the infield due to his ground-ball tendencies, and they’d probably be wary to give that up for the rover (and of course this could never be implemented in double play situations). You’d probably want at least one plus defender at shortstop or third base to put this in action. But, given how infrequently Castellanos actually hits the ball on the ground, are three infielders on the left side really necessary? Castellanos beats teams with his liners, not his grounders, so isn’t it the liners teams should be looking to take away?

Still, for that very reason of having to give up the overshift to do this, it seems more likely to me that if (when?) we begin to see this implemented, it’ll start with left-handed batters, so let’s go there.

How about Gregory Polanco?

See, the nice thing about doing this to a lefty is you can keep the three defenders on one side of the infield, and cut down damage on balls in the air. And for someone like Polanco, who’s hit 60% of his balls in the air and sprays them all over the outfield while pulling two-thirds of his grounders, is that the worst idea?

And unlike Castellanos, Polanco truly sprays his air balls across the outfield. Liners get hit to both left and right. Pure fly balls get hit to left and right. And so rather than using the rover, we can use a similar outfield alignment to that which Lindbergh and Miller used — corners pinched in to cut down the extra-base hits in the corner, dual center fielders playing deeper to track down the extra-base hits in the gaps.

Admittedly, neither Polanco’s air-ball rate or ground-ball pull percentage were as extreme as Castellanos’, so he’s probably not the perfect candidate for this, but he was at least comfortably above average, making him our best left-handed candidate.

And then there was one more name. I couldn’t stop thinking about it. He checks all three boxes. He’s also an incredibly dangerous hitter. Maybe the most dangerous hitter. Everything teams have done in an attempt to get him out has failed, so why not this? Nothing else is working. He’s got parts of Castellanos’ profile, and parts of Polanco’s profile.

It sounds crazy, but is it? Should teams try the four-man outfield on Mike Trout?

I was surprised to learn that Trout pulls a higher percentage of his ground balls than anyone in baseball — 80%. There’s been less need for a second baseman against Trout than any other right-handed hitter. Not only that, but he has an above-average rate of air balls (59%) and he truly sprays them all over the outfield with both liners and flies.

Now, almost definitely, you’d want a plus shortstop and/or third baseman — the thin line of green dots in left field suggests he’s already hitting grounders through the overshift. And, as Miller pointed out on a recent episode of Effectively Wild on which I appeared to discuss this subject, there’s plenty more to this all than just the batter’s tendencies. The pitcher’s tendencies are equally important — you’re not going to go to a four-man outfield with an extreme ground-baller like Dallas Keuchel on the mound. Handedness matters, too. The ballpark is important, as well — Buster Olney toyed with the idea of implementing a four-man outfield in Coors this offseason due to its spacious outfield dimensions. A commenter suggested that the ideal location for the five-man infield might just be Fenway Park, with the Green Monster essentially serving as the third outfielder.

But, in a vacuum, how many extra bases might that fourth outfielder save with Trout at the plate? How many doubles and triples become singles? Does it outweigh the number of singles that squeak through the left side with two defenders in the dirt as opposed to with three? Just looking at the spray chart, it doesn’t seem as crazy as it might sound. In fact, I hereby dare an MLB team to put the four-man outfield on Trout with a fly-ball, right-handed pitcher on the mound in a spacious ballpark this year. Hey, it’s not like the matchup can get much worse than it already is.