A four-man outfield: last positioning gambit or the new norm?

With the 2019 MLB season about to start, a whirlwind of uncertainty surrounds the game.

Firstly, the second year of cold ‘hot stove season’ with limited free agency signings happening has lead to open discussion of action by the players’ union. The addition of extension signings by younger players buying out arbitration and free agency years adds to this interesting dilemma.

Secondly, we have the news that Major League Baseball and the independent Atlantic League announced a partnership to test certain rule changes that could be coming to MLB. One of which is already set to be implemented in 2020: the three batter minimum rule. There are seven rules in total which are to be implemented but the one I want to focus on here is the following.

Require two infielders to be on each side of second base when a pitch is released (if not, the ball is dead and the umpire shall call a ball)

This would ban any infield shift that put a third infielder on either side of second base. But a team could theoretically set up a player to be right on the base and shift over as soon as the pitch is thrown which would cause some issues for the umpires watching the situation.

Like the play above, a lot of shifts have the third player barely in the other half so they could quickly move over to get into the correct position. It will be interesting to see how this plays out and how the umpires will rule.

But while this still isn’t implemented in MLB, some teams are going to continue to think outside the positioning box and the area to explore, innovate and experiment is no longer in the infield.

This offseason Bryce Harper has made the news various times thanks to his protracted free agency saga but continued to make the news as he made his very first appearance for the team. When he stepped into the batter’s box for the first plate appearance of his Phillies debut, Blue Jays third baseman Eric Sogard moved to left field, giving Toronto four outfielders and three infielders positioned to the right of second base.

The four man outfield isn’t unheard of but it only happened on 251 out of 716,812 pitches in the regular season last year. Lucas Duda faced the most with 55 pitches over 15 PA. In fact it has already happened to Bryce again with the Rays setting up like this a few days later. So, why do some teams do this?

The logic isn’t that dissimilar from the infield shift but the hitting profile required is slightly different. For this to be effective you have to remove an infielder from a position you don’t expect a hitter to hit to and place him in an area he would hit more balls to.

If an opposition hitter has a low opposite field GB/LD rate you can remove the infielder from that position and if they have a high fly ball rate you can move it to the outfield instead of onto the other side of the infield, for a standard shift.

Previous research has shown that fly ball rates and opposite field GB/LD rates are predictive from one year to the next. If this wasn’t true teams wouldn’t do the normal infield shift. Therefore we can make an assumption on 2018 data about which players may hit like this in 2019. So who should be we be throwing extra men into the outfield for?

Note, these fielding manoeuvres are most likely to be used in and suggested for bases empty scenarios. Men on base complicate the whole calculation due to the need to cover the bases.

The graph above shows all the hitters who had more than 100 batted balls in 2018. It plots their opposite field groundball/line drives (GB/LD) rate against their flyball rate. 

I have highlighted the players I believe this could be utilised for. I have also highlighted Duda and Harper as both of those are not among the players which the profile matches best to this but are still high on the list of potential candidates.

The top trio of Matt Carpenter, Joey Gallo and Eric Thames all hit fly balls more than 35% of the time and opposite GB/LD less than 5%. The mean for these hitters is 12.8% opposite GB/LD and 23.4% flyballs and the standard deviations for these are 3.5% and 5.1% respectively.

As these three are all left handed hitters, they are prime targets for the 4-man outfield as you are most likely removing the third baseman. If they were righties you would want to remove the first baseman but that opens up lots of issues around someone getting to first for a grounder.

So we have identified who we should use extra outfielders for, the question is now what do we do with our extras and how should all the outfielders like up. To do that we should look at the spray charts for these players. Thanks to Smada and Prospects Live there is a simple online tool we can use.

These three all identify the same area which the extra outfielders should be put: short right field not too far from the foul line. If we remove the third base fielder all of the outs which are inside the diamond between second and third would be singles. However for all three hitters there are more singles and double which would be converted into outs in short right. These three even have a hitting profile that a team might want to infield shift and put a fourth man in the outfield as such a small amount of batted balls go between second and third base.

Teams continue to look for every edge they can get. This is known in cycling and other sport as ‘marginal gains’ – the philosophy of improving everything possible by small amounts in order to separate you from everyone else.

There are far less hitters that match this profile than the one required for the standard shift. But with 15-20 who do I would be very much surprised if we see less four-man outfields in 2019 than we did in 2018 but it won’t be anywhere as near as common as the infield shift.

With the league looking like it doesn’t want to allow these changes to happen if it damages the game as a whole, the teams will be looking to be a few steps ahead of the league on whatever gains they can get. So expect more changes from the normal dynamic this season.

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