Welcome to the Windy City, Yonder Alonso by Mike Podhorzer December 17, 2018 The flurry of trades and signings has continued, this time with the White Sox getting into the action. The Pale Hose traded a minor leaguer to Cleveland for first baseman Yonder Alonso, despite the fact they already possessed a perfectly good first baseman who they don’t intend to trade. But whether Alonso or Jose Abreu play first and the other DHs doesn’t really matter, except during interleague games, which means it’s likely that Alonso will lose some plate appearances. How might the move from Progressive Field (Cleveland) to Guaranteed Rate Field (GRF – Chicago) affect Alonso’s offense? Let’s check in with the 2017 park factors. Park Factor Comparison Team SO BB GB FB LD IFFB 1B 2B 3B HR Basic Indians 100 100 101 97 101 92 103 107 83 105 104 White Sox 102 103 98 101 98 105 96 93 102 108 99 After five seasons of weak performance for a first baseman between the Padres and Athletics, Alonso embraced the fly ball revolution in 2017, finally breaking out offensively and displaying the power expected from a corner man. While he couldn’t quite keep up those newfound skills in 2018, he still held onto some of his power gains en route to his second highest ISO, HR/FB, and fly ball rate marks of his career. So now the question is whether he’ll ever again regain his 2017 form and whether GRF will get credit with an assist. Comparing the plate discipline metrics, the two parks don’t diverge too drastically, but Progressive played neutral for strikeouts, while GRF inflated them by 4%. On the other hand, GRF boosted walks by 6%, while Progressive was neutral. So GRF is more of a three true outcomes park than Progressive. Alonso always posted strong strikeout rates until that mark spiked along with his power starting in 2017. His walk rate has been up and down, but overall, he has walked a bit more often than the league average. The park factors are unlikely to have much of an impact, as the possible slight increase in strikeouts could be canceled out by the increase in walks. Onto batted ball type factors, we find that Progressive wins here with a slightly inflationary line drive factor, while GRF suppresses the best type of batted ball. Progressive had even more of an advantage with pop-ups, as the park reduced them by 16%, while GRF actually boosted them by 10%. That’s an enormous swing. Alonso has always been a pretty solid line drive hitter, while he’s coming off the highest IFFB% of his career. His chances of rebounding and pushing that back down to his career average takes a hit with the park switch. Combined, these factor changes could hurt Alonso’s BABIP. Lastly are the various hit categories, where we see a split decision. Progressive is much more favorable for singles (another BABIP advantage) and doubles. Luckily, Alonso hasn’t been much of a doubles hitter, so I can’t imagine he declines from such a low base. The singles factor, though, is another mark against his 2019 BABIP. On the positive side, Progressive really suffocates triples, while GRF boosts them marginally. Ha, it doesn’t matter, as Alonso has hit a whopping two triples his entire career. For reals this time, the true positive is an even higher home run factor than he enjoyed at Progressive. In 2017, GRF was the fifth most favorable home run park for left-handed hitters. Progressive was also a haven for left-handed home runs, but not nearly to the same degree as GRF. Overall, you might be surprised to learn that Progressive was a strong hitter’s park in 2017. Even more surprise is that GRF was actually slightly pitcher friendly overall. Of course, the “Basic” factor is overall and not broken down by handedness, so it’s likely the specific overall handedness factors paint a slightly different picture. So to sum things up, the batted ball type and hit category factor changes are going to be a negative for Alonso and hamper his BABIP. On the other hand, he might hit an extra homer or three in his new digs. I would say the effects on his fantasy line is a wash, as he might be trading some BABIP for power. Therefore, I don’t think this move changes his value solely due to the park switch. However, because he now might sit more often in NL parks, he does lose a buck or two in value because of the playing time situation.