It’s True, It’s True, It’s Finally True! Mookie Betts Officially Switches Coasts

In what turned out to be quite soap operatic, the Red Sox and Dodgers finally complete a trade…though not exactly the original one that was tentatively accepted last week, which also included the Twins. The biggest name to move is of course Mookie Betts, who makes what was already an excellent Dodgers offense into one that is now laughably good. But for those who have already spent a first round pick on Betts, plan to keep him, or are wondering how to adjust his value after the move, the big question now is how might the switch in home park affect his performance. Let’s consult the park factors (2018) and find out!

Holy guacamole, it’s a rout! I did not expect this. Let’s get down to specifics.

We’ll start with the hit type factors. The quirky dimensions and the Green Monster at Fenway Park make things really interesting for hitters. Certain types of hitters also thrive more than others, like lefties who are able to poke flies the opposite way off the huge wall for easy doubles. For singles, Fenway boosted them by 6% (remember these park factors are halved to account for half the games being at home), while Dodger Stadium (DS) actually suppressed singles by a meaningful 8%. That’s a large swing in a park factor that their typically isn’t a huge swing in.

Like many hitters, Betts’ BABIP has bounced around, hitting a low of just .268 back in 2017 and then following that up with a career high exactly 100 points higher at .368 the next season. For his career, his BABIP stands at .314, which is definitely above the league average. But given his combination of power and speed, along with his home park, you may have expected a bit more. He does own a career home BABIP of .333 versus .295 in away parks, which validates the help he has received from hitting at Fenway. Obviously, the park factors confirm the move is likely to hurt his BABIP, and resulting batting average.

The Green Monster makes it heavenly for left-handed doubles, as the park easily sports the highest factor. Betts isn’t a lefty, but the park still tied for second in baseball in doubles factor for right-handers. It’s nowhere close than for left-handers, but still quite friendly. Unfortunately, DS is merely neutral for doubles, another potential hit to his BABIP. Betts is actually a big doubles hitter, having swatted at least 40 of them in every full season of his career. Losing four to five could cost him a bunch of runs batted in and a couple of runs scored.

Neither park is good for triples, but DS was actually the worst park in baseball, by far, in 2018 for them by both righties and lefties. Betts has hit five in each of the past two seasons, so perhaps he loses one or two this year, which could cost another RBI and/or run scored.

Rounding out the hit type factors, we finish with home runs. This is actually the closest, but once again, DS suppresses them, while Fenway slightly increases them. Surprisingly, Betts has posted an identical HR/FB rate in home and away parks. I think the bigger factor driving his homer rate is whether 2018 was the fluke or a skill level he owns that he’s capable of returning to. Since he hits a ton of fly balls, a change in HR/FB rate could really affect his homer total.

The strikeout rate factors are nearly the same, while both parks suppress walks. DS does so far more significantly, which is going to make it even more difficult for Betts to continue his streak of increased walk rates, the last two seasons of which were over 13%.

Last are the two batted ball type factors. However it does it, Fenway has boosted line drives, while DS has reduced them. Betts’ LD% has been up and down and overall his career average is close to the league. A decline would also hurt his BABIP. Furthermore, DS inflated pop-ups (IFFB) to a greater degree than Fenway did. Because he hits so many flies, Betts actually hits an above average rate of pop-ups. Yet another hit to his BABIP potential.

Finally, we end with the “Basic” factor which is the overall park factor, though that includes left-handed batter effects. It confirms that Fenway is a much friendlier environment to hit in than DS, which plays as a pitcher’s park. While moving to another excellent lineup will soften the blow, the park switch is a clear negative for Betts’ performance. His RBI total will also take a hit since the ninth man in the lineup is typically the pitcher, so there will be fewer opportunities for batters to get on base ahead of him. Betts is obviously still a first rounder, but this move definitely shaves some dollars off his value (I would guess like $3-$4, which could knock him behind a couple of guys in the first round).