But the bad fielding player was not actually a bad fielder in the first place if his metics are taking a hit primarily for plays not made that would have been made. That’s the point. Just because the defensive component of WAR says you’re something doesn’t actually make you that something especially in the case of outfielders.
It’s a real consequence of the (serious) limitations of calculating defensive component of WAR, also one of the reasons defensive WAR can fluctuate so much year-to-year...and again, it’s worse for outfielders.
These same range factors also tend to boost defensive WAR for almost any player who gets to play the center field role, including players that have ‘average-ish’ speed. And that’s helped Kepler’s defensive metrics. You’ll notice that Kepler’s defensive WAR has trended up in years where he has played relatively more games in center.
I don't think that how this works?
Kepler's boost comes from the positional adjustment made for playing CF over a corner OF spot, because it's a more difficult position to play defensively.
but Rosario didn't get punished for Buxton (or kepler) "stealing" opportunities to make plays. he got punished for not making plays on ball in his area, ones that an average corner OF would make. that makes him a poor fielder.
Rosario had pretty good range/speed when he first came up, and while he's always had some of those "what the hell?!?" moments catching the ball, he did pretty well getting to things and making the plays and enhanced his defensive stats and reputation with a strong arm. As he's gotten older, he's gotten slower and he gets to fewer balls. He's still capable of having a solid season defensively (he was fine last year in a smaller sample, and had a pretty good season in 2018 on the defensive side too). but he was pretty bad in 2017 & 2019.
If he's fully healthy and in shape he might be able to have a good season defensively but that's what's going to drive it, not being "freed" from playing next to Byron Buxton.
setting the over/under at 2 bWAR is a pretty fair number; He's cleared that in 2 of his 6 MLB seasons, but was on track for it in the pandemic shortened year as well. I think he's probably going to end up around there, which for Cleveland would be a win; they've really struggled to get consistent production from the corners, especially both at the same time. (looking back at their WAA you see a lot of results where if LF is top 10, then RF is bottom 10 and too many negative numbers overall)
I think Rosario helps Cleveland this year and is a solid asset at $8M. (I don't think there was ever a realistic opportunity for the Twins to keep him at that number) He should hit enough to give good value at that price, and I think his defense will depend on how his legs hold up over a full season. Might be solid, could be pretty bad.