How hard balls are hit is taken into account in UZR. The main problem with fielding % is that it is almost completely dependent on one person to make a judgement and can actually hurt better defenders. If you have good range you can make errors that a worse/slower defender wouldn't even be able to get to. The other problem is that even very crappy defenders like Braun cna have a good fielding% because unless you drop a ball you are almost never going to get an error. So in the case of outfielders, fielding % is almost totally useless. Unless a guy has an extremely bad fielding % it doesn't give enough information to be very useful because most players fall into a small range. If you have range and get to a ball but can't make a play on it, it usually doesn't have any difference in outcome than if you can't get to the ball. That is correct. However fielding % would actually punish a guy for getting to a ball and not making a play on it. UZR gives some credit for range. I've felt that UZR is biased against leftfielders. The reason is because a majority of hitters are right-handed, and when they pull the ball it is usually hit much harder than if they hit it to center or RF. The harder it is hit, the less time you have to get to it; the less time you have to get to it the less balls you get to, which impacts UZR. I don't think that all LFs are outstanding defenders, but I don't think they negatively impact the outcome of games as much as some think. When I saw last year that Fangraphs had a higher value on Nyjer Morgan than Ryan Braun... well, that's all I needed to know about their valuation system. I don't think that is a problem with UZR. That is more of a WAR or more specifically the positional adjustment of WAR issue. For the most part you get a bonus for playing a harder position. I can't argue against it much since most LF couldn't play in CF very well. I could be mistaken but as a LF your defense is set at zero by other LF. You sont' get compared to CF or RF.