Teoscar Hernández Joins the Mariners by Mike Podhorzer January 18, 2023 Back on Nov 16, the Mariners acquired Teoscar Hernández from the Blue Jays to beef up their offense. After spending the majority of his career with the Blue Jays, how might the move to a new home park affect his performance? Let’s consult the park factors and find out. Park Factor Comparison Park (Team) 1B as R 2B as R 3B as R HR as R SO BB GB FB LD IFFB Basic Rogers Centre (Blue Jays) 99 101 96 106 101 98 101 101 100 97 99 T-Mobile Park (Mariners) 98 94 86 102 103 97 98 102 94 102 95 It’s a clean sweep, folks! You don’t often see this, especially when neither of the parks are on the hitter or pitcher friendly extremes of any of the factors. Let’s dive into the individual factors now to see how Hernández’s performance might be impacted. We start with the non-home run hit type factors, in which T-Mobile is more pitcher friendly than Rogers for each of them. The singles factors are actually pretty close though, with each suppressing them slightly, but T-Mobile doing so slightly more. Hernández has been a darn good BABIPer throughout the majority of his career, posting a sub-.300 mark just once over a full season. Interestingly, he has posted a significantly higher BABIP on the road than at home. His .335 BABIP in away parks is far above his .317 home mark. That’s huge and surprising, especially since Rogers only marginally reduces singles. Even odder is that Hernández has hit a higher rate of line drives at home than away, and yet has posted a lower BABIP. Given the home/road split he has experienced, it’s hard to imagine his BABIP would be hurt even more moving to T-Mobile. Moving along to doubles, we find that T-Mobile significantly reduces them, while Rogers increased them slightly. Hernández has posted similar doubles rates at home and away, but the park switch could reduce his doubles rate a bit. Finally, both parks suppress triples, but T-Mobile significantly so. He’s only hit 10 triples in his career, so the park switch is unlikely to impact his 2023 total. Now let’s get to the home run factors. We find that both parks actually inflate right-handed dingers, which surprises me as I didn’t think that T-Mobile did. Hernández has posted pretty similar HR/FB rates at home and away, despite his home park being pretty home run friendly. That surprises me too. That said, his HR/FB rate projection should definitely be reduced in a less home run friendly home park. Next up are the strikeout and walk factors. Both parks inflated strikeouts, but T-Mobile was more inflationary last year. Hernández has posted very similar strikeout rates at home and away, with a slightly higher mark at home. Perhaps his strikeout rate forecast should rise slightly with the park switch. The walk rate factors are similar and both indicate the parks suppress them. Hernández has walked a bit less at home, and given the similar factors, his projection shouldn’t change much. We now shuffle on over to the batted ball type factors. T-Mobile suppresses grounders and inflates fly balls, but only marginally more than Rogers did. Hernández posted the highest GB% and lowest FB% of his career last year, so the park switch may help him revert back to his previous fly ball ways. What’s interesting here is that Hernández has seen his FB% decline for five straight seasons. That’s head-scratching for a power hitter like him. The two parks are pretty far apart on the batted ball type factors that will definitely impact his performance. T-Mobile significantly suppresses line drives, versus a neutral effect by Rogers. Since he has posted a far higher LD% at home, this could reduce his BABIP. Similarly, T-Mobile inflated pop-ups, while Rogers suppressed them. Hernández actually posted a higher IFFB% at home throughout his career, but still, his forecast should increase his IFFB%, also affecting his BABIP negatively. Finally we end up on the five-year Basic run scoring factor. Both parks rate as pitcher friendly, but T-Mobile far more so than Rogers. With worse factors affecting BABIP and a lower home run factor, the home park switch is very clearly a negative for Hernández’s fantasy value.