Eric Hosmer signed with the Padres…wow, was it only last weekend? Eric Hosmer signed with the Padres last weekend. I wrote up the whole post, and then sat back, eager to look at the comments, given how Hosmer is so famously polarizing. And, yeah, those expected comments rolled in, just as you’d think, but there was also another comment that stuck in my head. Here is most of it:

Maybe it’s kind of obvious, when you think about it, but we probably haven’t given it enough consideration. With all the tools we have, it’s been easy to dream on Hosmer’s power upside. Similarly, it’s been easy to dream on Christian Yelich’s power upside. This is supposed to be the era of data-driven player adjustments, so you can imagine a version of Hosmer and a version of Yelich who are able to generate consistent loft. But this isn’t as easy as it seems. It’s not even necessary, and there’s always the chance a change could backfire. See, the thing about Hosmer and the thing about Yelich is that both of these hitters are already good.

Let’s quickly explore some familiar territory, using information from Baseball Savant. Why have people keyed on Hosmer and Yelich in particular? Here are 2017 average launch angles and exit velocities, for everyone with at least 100 batted balls tracked.

The two players in question are in yellow, and Yelich is the yellow point further to the right. Yelich just ranked in the 94th percentile in exit velocity, but he ranked in the 8th percentile in launch angle. Hosmer, meanwhile, just ranked in the 87th percentile in exit velocity, but he ranked in the 4th percentile in launch angle. The data is encouraging and discouraging at the same time. The contact quality is good! But these guys seem to hit grounder after grounder. What if they could put more balls in the air? It’s like talking about Yandy Diaz, except with two established big-league regulars. (Diaz is the point on the baseline, furthest to the right.)

This brings to mind the phenomenon of swing-changers. Or, if not always swing-changers, then approach-changers. So much attention has been focused on the success stories. But, try to rattle those successes off, off the top of your head. Of course, there’s J.D. Martinez, and there’s Justin Turner. There’s Josh Donaldson, and there’s Jose Bautista. Daniel Murphy made a change. Marlon Byrd made a change. Logan Morrison made a change. Yonder Alonso made a change. Elvis Andrus made a change. There are others — this list isn’t exhaustive — and each case is inspiring, but each case also seems to have something in common. Before changing, the hitters weren’t very good. Some of them were fighting to just extend their careers. There are two things to surmise: These players were incentivized to try to adjust, and they also had some room to grow. Their old swings must not have been optimal.

At 28, Eric Hosmer is a veteran. He’s an above-average hitter, and his wRC+ last season was 135. The Padres paid a fortune to land him. At 26, Christian Yelich is also now a veteran. He’s an above-average hitter, and his wRC+ last season was 115. He was hurt by his home ballpark, and the Brewers paid a fortune to land him. Hosmer knows he’s good, and he knows he was wanted. Yelich knows he’s good, and he also knows he was wanted. There’s less incentive for these players to change. There’s also less incentive for their teams to try to change them.

The Padres and the Brewers know all about Statcast. And I’m certain the players know all about launch angles. They’re probably tired of hearing about launch angles. It’s not that they couldn’t imagine a better performance. But there would be some resistance and hesitation here, on both sides. Swings and approaches are fundamental to what a player is, so why risk messing with a good thing? How aggressively should you chase after upside? And how much upside is even really in there?

It’s funny — there are plenty of cases of mediocre players who made approach changes and improved significantly. There are far fewer cases of good players doing the same thing. Now, part of the explanation there is obvious. But, take Francisco Lindor. He just hit a ton more fly balls, and his wRC+ hardly budged. The same thing has been true of Matt Carpenter, after his mid-career approach overhaul. Joey Votto and Mike Trout have had some fluctuations in approach over time, but they keep putting up basically the same numbers. And you can even look at Yelich himself. The past two years, he’s hit fewer grounders than he used to. As more of a ground-ball hitter, his wRC+ was 119. As less of a ground-ball hitter, his wRC+ has been 123. How much does that mean?

And sometimes good players can get in trouble. Gregory Polanco has suggested that trying to hit more fly balls messed him up. Jason Heyward chopped his ground-ball rate in 2016, and he was awful. This past year, Wil Myers hit more balls in the air, and he was less productive. It’s not as if it’s impossible for players who are already good to get better. It does happen. But it’s not a simple process. In order to be a quality hitter in the major leagues, you need to be almost unbelievably good. Players who are good hitters probably already have swings that are more or less what they need to be. Maybe that’s not always the case, but there’s real risk in attempting a major adjustment. You never know when a hitter might become terribly uncomfortable, having succeeded in one way for multiple years.

When you have someone on the fringe of the bigs, you might get more buy-in for an adjustment, and you might be more likely to uncover something positive. J.D. Martinez’s original swing clearly wasn’t working for him, but the talent must’ve always been in there. When you take someone like Hosmer, his swing has been working for him. So the player is less incentivized to make a change, and the team is less incentivized to suggest one. Hosmer might’ve already found the approach that works best for himself, because being as good as he is is already impossibly hard. The same goes for Yelich. There are ways for these players to get better still, but there would be enormous risk in trying to rebuild how they bat.

Doesn’t mean something won’t change. Doesn’t mean something won’t change for the better. It’s just nothing to expect. Based on some numbers, it seems like Hosmer and Yelich could improve by aiming up. I’m sure their new teams have thought about it. There’s just not much in the way of precedent here. It’s not the good players who’ve had to save their careers.