Juan Soto Switches Coasts, Heads to San Diego – A Park Factor Analysis

Holy guacamole, what a blockbuster! On Tuesday, the Padres acquired superstar Juan Soto to bolster a middling offense that has been without Fernando Tatis Jr. all season. Let’s consult the park factors to find out how the park switch may affect Soto’s performance.

In the above table, I have highlighted the more hitter friendly park factor. Before diving into each individual metric, you can see that Nationals Park was more hitter friendly in five factors, versus just three for Petco Park.

Let’s start with the hit type factors. Did you know that Nationals has dramatically inflated both singles and doubles, while Petco has suppressed singles? I didn’t! Those are meaningful differences. Nationals actually ranks tied for third highest in left-handed singles factor, while Petco ranks tied or seventh worst. That’s a big difference and could have an effect on Soto’s BABIP over a large enough sample to tease out the park factor. Heading into this season, Soto has consistently posted strong BABIP marks, peaking at .363 during the short 2020 season, and averaging a .330 mark during that time. He was even better at home, posting a .340 BABIP during that period. But this season, he has struggled, as his BABIP has plunged to just .243, thanks partly to a career worst 14.3% LD%. At home, he has posted just a .230 BABIP, despite the park’s inflationary factor.

Because he has suffered such a decline in BABIP and his LD% has collapsed, we would figure both marks would rebound, at least somewhat, regardless of where he plays his home games the rest of the way. So it’s going to be tough to determine how much of an effect Petco’s BABIP suppression factor ends up playing a role. Obviously, it’s not a positive, but regression to Soto’s mean is likely to have a greater effect the rest of the way, more than offsetting the park effects here. That said, his rebound may have ended up being greater had he stayed in Washington.

Moving along to home runs since the triples factors are nearly identical, we find that Nationals is surprisingly one of the better left-handed home run parks in baseball, as it ranked eighth. All the other parks, except perhaps Angels Stadium, are perceived to be home run friendly parks. You don’t think of Nationals being one of those, or at least I didn’t. On the other hand, Petco suppresses left-handed home runs, ranking 9th worst in factor. That’s a significant swing. For a hitter who owns big power with a career HR/FB rate over 20%, this is meaningful.

Soto’s HR/FB rate is at a career low at the moment, and oddly, he has posted a massively higher mark in away parks than home parks during his career — 29.3% away and 19.8% at home through 2021. This year, his splits are almost identical, though the sample is much smaller. It’s very surprising to see such stark splits, since hitters generally hit better at home, plus his home park boasts a left-handed home run factor that ranks tied for sixth. This is a good example why one blanket park factor, even if split by handedness, isn’t ideal for every hitter. It’s hard to believe this is randomness due to the wide gap, so clearly Soto’s home run hitting style doesn’t mesh well with Nationals Park. Seeing this, perhaps he won’t suffer as much of a HR/FB rate decline as the park factors would suggest.

Next, let’s talk strikeouts and walks. The strikeout factors are fairly similar, but Petco marginally inflates them, while Nationals suppressed them. Soto has posted a slightly lower strikeout rate at home throughout his career, while the walk machine has also taken a free pass at a slightly higher rate at home. I can’t imagine him walking even more at Petco, despite the slightly more friendly walk rate factor! That OBP is going to be a boon to whoever hits behind him though.

Since there is no “good” groundball and fly ball park factor, they didn’t get highlighted. The line drive factors are similar, with Petco being slightly more hitter friendly. As toucher on earlier, Soto’s LD% has declined to a career low, and he’s never been a big line drive hitter to begin with. The factor difference here probably won’t have much of an effect, so we’ll assume he’ll just rebound naturally close to his career mark.

The IFFB (pop-ups) factors are also nearly identical, with both parks slightly suppressing them, which is good for BABIP. Soto’s IFFB% has risen to a career high this year, which when combined with a career high FB%, means the highest pop-up rate of his career. In fact, he’s already hit the most number of pop-ups in a season, the first time reaching double digits. That’s another driver of his down BABIP.

Finally, we arrive at the overall five-year factor. Interestingly, despite boasting park factors that inflate singles, doubles, and home runs, Nationals Park only grades out as slightly offense inflationary. I would have expected a bit of a higher Basic factor based on the hit type factors. On the other hand, Petco’s offense suppression makes sense, and it ranked as the fifth worst park for offense.

So overall, the park switch is clearly a downgrade for Soto’s production. It’s seemingly negative for both his BABIP and HR/FB rate. However, he’s sporting a career worst wOBA (still .390 though!), driven by the lowest LD% and BABIP of his career, along with the lowest HR/FB rate. So any forecast would expect him to increase his BABIP and batting average, and knock more of his fly balls out of the park. That expected rebound is likely to overshadow any effects from the park switch, but that doesn’t mean the park switch won’t have an effect. It’s just going to be more difficult to isolate.