If the Cardinals are able to complete their acquisition of star third baseman Nolan Arenado – under the terms as we know them now – they’ll add the best defensive third baseman of his generation. Kyle Newman of the Denver Post pegs the Arenado deal as the biggest trade in Rockies’ franchise history. Cardinals shortstop Paul DeJong certainly sounds pleased, saying on MLB Network Radio today (via Twitter), “…having a guy like Arenado in our lineup is going to completely change the way pitchers look at us.”

Arenado’s trophy case is full: five All-Star nominations, four Silver Slugger awards, and a Gold Glove for every season in the Majors (eight). A career .293/.349/.541 hitter, Arenado has created 39.1 bWAR/32.3 fWAR with a solid 7.9 percent career walk rate and solid 15.0 percent career strikeout rate. Though 2020 was a down year offensively, he became one of the toughest hitters in the game to strikeout, doing so in only 10.0 percent of his plate appearances.

All that said, he would head to Busch Stadium III with the usual caveats of a player leaving Coors Field. Namely: can he hit outside of Coors?

Paul Goldschmidt can walk Arenado through the transition from face-of-the-franchise in the west to being just “one of the guys” crashing at Yadi Molina’s house. But to preview the shock-to-the-system Arenado may face taking his hacks so much closer to sea level, we can go a little further back to another Rockies’ superstar who went east for the latter half of his career: Matt Holliday.

Holliday averaged 154 wRC+ per season during his first five years at Coors Field, his age-24 to age-28 seasons (2004 to 2008). Over that same time span he posted 105 wRC+ on the road. For his part, Arenado is a career 128 wRC+ hitter at home and 108 wRC+ hitter away from Coors.

Visual learners can check this Fangraphs chart for his home/road splits by age, then do the same for Holliday. Holliday’s splits look nearly the same through age-30 before converging at the point in his career that Arenado faces now: 30 years-old and permanently changing his address from Denver to St. Louis.

As you can see in that chart, Holliday’s overall wOBA follows a fairly traditional aging curve. Playing at Coors Field, however, can warp the shape of that production. As this March article from the Athletic’s Nick Groke covers in detail, the Coors Field dilemma isn’t just about how fast the balls fly through Colorado’s thin air, but how much sharper the breaks appear to hitters on the road. As much as Coors helps a hitter’s numbers (more than a normal home split), playing away from Coors hurts (more than a normal road split).

To think in terms of wRC+, it might just be that the Arenado who arrives in St. Louis will no longer be a 128 wRC+ hitter at home and a 108 wRC+ hitter on the road – but he could still be a 118 wRC+ hitter overall.

Or at least, that was Holliday’s path. Over his seven years in St. Louis, his home/road splits stabilized. He would average 133 wRC+ on the road and 142 wRC+ per season at home. On the whole, he arguably became a better hitter with 133 wRC+ during his five seasons in Colorado compared to 139 wRC+ in his seven full seasons in St. Louis. Does that mean Arenado will do the same? Of course not. Just because Holliday stayed largely healthy and productive past his prime years doesn’t mean that Arenado will do the same.

Holliday and Arenado tracked mirroring paths to the Show-Me State. Holliday’s age-29 season was anomalous for his career in terms of the playing conditions – just like Arenado. Whereas Arenado had to deal with a 60-game season in a pandemic-wracked world, Holliday faced the equally jarring reality of moving from Coors Field to Oakland’s spacious Coliseum. I kid, but Holliday’s half-season in Oakland stands out as a singularly odd year on Holliday’s resume in terms of the conditions relative to the rest of his career. If Arenado stays in St. Louis the length of his contract, he’ll be in Cardinal red for seven seasons from age 30 to 36 – the exact length of stay Holliday enjoyed in the Gateway to the West.

On the other hand, they aren’t the exact same type of hitter. While both are right-handed sluggers, Holliday had a little more in common with Goldschmidt than Arenado. Holiday was a worm killer even in his era. As a Rockie, Holliday logged a 1.38 groundball-to-flyball rate, whereas Arenado’s 0.87 GB/FB rate reflects the fact that he hits the ball in the air more than Holliday ever did. Compared to the rest of the league, Holliday hit the ball on the ground more than the average player throughout his career. Arenado can’t even see him from so far down the other end of that spectrum.

Holliday sprayed the ball to all fields a little more than Arenado, who leans pull side with 41.8 percent pull percentage to 23.1 percent opposite field for his career. Theoretically, that could hurt Arenado, as Busch tends to be a good singles and triples park for righties while suppressing offense in most other regards, per Park Factors at Swish Analytics. At least he’ll have a shorter porch in left to target, for what that’s worth.

Will Arenado adapt to his new confines? Ask Holliday, who not only tread this path before but was teammates with Arenado in 2018. He offers nothing but praise, writes Derrick Goold of the St. Louis Post-Dispatch.

Besides, Arenado’s glove should continue to be an exceptional asset. While age may diminish his abilities at the hot corner somewhat, he has a lot of wiggle room before even entering the stratosphere of any other third baseman outside, maybe, Matt Chapman. With DeJong on his left, he shouldn’t even face much of an adjustment there. DeJong may be one of the few defensive shortstops who can rival Trevor Story’s competence on that end.

Arenado is heading from an organization that has never won its division to one of the game’s premier, trademark franchises. He’s leaving the NL West, where the Dodgers and Padres are readying for what could be an epic divisional bloodbath – and he’s joining the NL Central, where contenders are being broken down and sold for parts. It might be a jarring move for Arenado, but he can always look back and take comfort in the fact that this trail has been blazed before – and it worked out quite well. Remember, it was only their second full season together that Holliday and the Cardinals won the World Series.