Comping Kris Bryant’s Rookie Season

Just as we all anticipated, Kris Bryant put together an extremely impressive rookie campaign. After he spent the season’s first two weeks in the minors, the Cubs set free their 23-year-old top prospect, and he proceeded to rake.  Bryant put up a .275/.369/.488 batting line on the strength of 26 long balls and a 12% walk rate, which yielded a 136 wRC+. Throw in that he graded out as a plus defender at third base, and the end result was a remarkable 6.5 WAR — easily tops among rookies, and was the 10th-highest figure of any hitter period. The Cubs seem to have a very special player on their hands.

We all knew Bryant had star potential long before he was called up. That’s why he got so much love on pre-season prospect lists, and also why KATOH liked him more than almost any other prospect. But now that he’s a year further along on that trajectory, we can be a bit more certain of what his career might look like. So, using this new data, let’s see what Bryant’s rookie campaign might tell us about what lies ahead. As I did yesterday in my piece on Carlos Correa, I performed a some weighted Mahalanobis distance calculations to generate a list of players whose seasons were most similar to Bryant’s. For more details on my methodology, see yesterday’s Correa post.

So, without further adieu, here are Bryant’s top comps according to my fancy computer math.

And here’s how the rest of their careers went.

Frankly, this isn’t quite what I expected. While several of these hitters had solid rookie campaigns, most of their careers weren’t all that memorable. Calling someone “a young Austin Kearns” isn’t exactly the highest of praises. All in all, this list is pretty disappointing, especially when held against Correa’s comps, which featured four Hall of Famers.

To be fair, though, some of these hitters turned out to be quite good. Bobby Grich, Mike Cameron and Troy Tulowitzki were/are bona fide stars. Danny Tartabull, too, was a prolific hitter for a long stretch — he just gave a ton of that value back on defense. But age wasn’t very kind to most of the other players in this group.

Billy Grabarkewitz’s career was derailed by injuries. Most notably, he injured his shoulder the following spring and was never quite the same. Mark Reynolds and Mike Young simply struck out too often to take full advantage of their power, and as a result, were toast after just a few years in the league. Austin Kearns was a way better player than I had remembered, but was still a disappointment overall. He had a strong rookie season, but his career trajectory was essentially a downward spiral until he was more or less replacement-level at age 28. Mel Hall and Greg Briley followed the Austin Kearns career path, only without plus outfield defense.

Here’s a look at these hitters’ career trajectories by cumulative WAR.

And by marginal WAR…

Since that last one was a little hard to follow, the graph below plots the group average and median, along with the group’s 25th and 75th percentiles for each year. Here’s how the group progressed through age 30.

That’s not a pretty picture. Does this mean Bryant will deteriorate into a platoon hitter by his 27th birthday? Certainly not. Keep in mind that this is just a narrow selection of players who happened to perform similarly to Bryant at s similar age. This is a small sample size, and as we all know, strange things can happen in small sample sizes. Furthermore, while these hitters were similar to Bryant, most of him weren’t quite as good as him. Bryant’s 2015 wRC+ was higher than nine of his 10 comps, and was much higher than a few of the hitters listed. So one could certainly argue that this analysis shortchanges him a bit. Even so, the downward sloping lines in the chart above are a little disconcerting.

Regardless of what the comps say, we know that Bryant is an excellent player today. We also know that he’s still just 23. Those two data points might tell you most of what you need to know. Good players have a tendency to stay good, especially when they’re not old, and Bryant’s already one of the best. It would be foolish to completely disregard this fact simply because Austin Kearns and Billy Grabarkewitz fell off of a cliff in their mid-20s. However, cases like those serve as sobering reminders that excellent rookies don’t always have excellent careers. And for what it’s worth, many of the rookies who were excellent in the ways Kris Bryant is excellent peaked at very young ages.