Core-five RBI: The frustrating search for a new MLB metric

Mar 19, 2021; Glendale, Arizona, USA; Los Angeles Dodgers infielder Zach McKinstry against the Texas Rangers during a Spring Training game at Camelback Ranch Glendale. Mandatory Credit: Mark J. Rebilas-USA TODAY Sports
Mar 19, 2021; Glendale, Arizona, USA; Los Angeles Dodgers infielder Zach McKinstry against the Texas Rangers during a Spring Training game at Camelback Ranch Glendale. Mandatory Credit: Mark J. Rebilas-USA TODAY Sports
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Mandatory Credit: Orlando Ramirez-USA TODAY Sports
Mandatory Credit: Orlando Ramirez-USA TODAY Sports

At the end of April, I had what’s known in the writing business as a “big idea.” It was inspired by a continuing anemic offensive performance by the Philadelphia Phillies – a modest streak of merely two runs a game. What was up with their core hitters? It came to me in a flash – honest – core-five RBI.

Wouldn’t the top five RBI producers be a team’s best hitters?

What was found by contrasting the performance of the Phillies and Los Angeles Dodgers was as follows – tentatively – with smallish samples: A top team like the World Series champion Dodgers has five players leading their RBI list who drive in between 0.67 and 0.70 runs apiece per game. A team hovering near .500 like the Phillies seemingly produces a figure around 0.53 RBI per leader per game.

Why not simply declare a new metric like core-five RBI? Is the idea dead, dying, or kind of breathing better?

Aggregate figures for about a month and then a work week (five games) for both teams were examined in this preliminary “study.”

But were the conclusions true? Was the difference between a world-beating MLB team and a mediocre squad really as narrow as a fifth of a run (0.20) per RBI leader (or one run per five-leader group per game)? Additionally, could five hitters actually predict a team’s success regardless of the strength of the team’s pitching and fielding?

That couldn’t be, could it?

What else was tentatively learned by looking at two contrasting teams? The very small team samples (four) examined shortly before Mother’s Day – merely two teams – very tentatively suggested that a .500 team could have a more stable core-five RBI group, but the top team might have perhaps seven or eight players battling to be part of the leader group of five.

In other words, the Phillies’ top five “qualified” hitters at the end of a month and at the end of the subsequent week were the same five guys. They drove in a consistent 0.53 runs per player per game.

The Dodgers, on the other hand, had an unqualified hitter in their top-five RBI group near the end of April (producing 0.70 runs per player per game), but two unqualified hitters in their top five after the end of roughly five weeks of the season (0.67 runs). The unqualified hitter in both samples, rookie Zach McKinstry, was driving in 0.82 runs per game before an injury shortly before May Day.

It shouldn’t be a shocker that really good teams find guys who drive in lots of runs despite not even playing every day, right?