Last week longtime RAB reader and commenter whozat shot me an email asking me if there was any reason to expect Brett Gardner to develop into a better Major League player than Joey Gathright. The comparison between the two players obviously makes sense since they’re both speedy outfielders who don’t hit for much for power, except that Gardner is called gutty and gritty because he’s white while Gathright is called exciting and athletic because he’s black. I noted in my reply that Gardner had hit for more power in the minors, but overall they had similar career paths and I really wouldn’t expect Gardner to be all that much better than Gathright in the future.
However, I took a deeper look at the numbers over the weekend, and there aren’t many similarities between the two players beyond physical attributes. One obvious difference is that Gardner was a third round draft pick out of a solid college program while Gathright was a 32nd rounder after the then-Devil Rays found him in a Louisiana adult league. Luckily though, the two players took an extremely similar path to the big leagues, although Gathright’s career began four years before Gardner’s.
Both players were drafted at age 21 and then assigned to a low level squad in the minors (Gardner went to the short season NY-Penn League, Gathright to the Low-A South Atlantic League). Both players started their age 22 season at the High-A level and earned a midseason bump to Double-A, then started the next year back at Double-A before being promoted to Triple-A in the middle of the season. In their age 24 season, their third full professional season, each player started the year in Triple-A before being called up to the big leagues during the summer and finishing the year there. It’s amazingly awesome and convenient that both guys spent their same age seasons at the same levels (and had similar plate appearance totals, no less) despite all the promotions. It made this analysis a ton easier.
I’m going to use three factors to compare Gardner and Gathright: Isolated Discipline, Isolated Power, and Stolen Base Success Rate. Isolated Discipline (or IsoD) is OBP minus AVG, and measures a player’s on-base skills beyond batting average. Isolated Power (IsoP) is basically the same thing except with SLG instead of OBP, and measures a player’s extra base hit power. Stolen Base Percentage is what it is, that’s self-explanatory. Let’s start with the most important thing, on-base skills.