You're somewhat nitpicking, but the truth is a player's talent level is ALWAYS changing.

tRA doesn't necessarily show true talent level. As the primer explains, the rates can regress a lot so tRA* is the best measurement of true talent level (of a season).

tRA* is not a measurement of a pitcher's results per se, but should be seen as the system's best estimate of a pitcher's true talent level based on his stats in any given year at any given level. tRA* does not consider a pitcher's statistics from other years and leagues.It's flawed. It also only considers offense for position players.And another is why does it seem like VORP is used so rarely? I really like the stat but it seems like its just never used.

Well say you're using a projection system. Perhaps ZiPS and FIP. Since FIP is defense independent, you can use fielding projections to add or subtract to the runs. Say a guy's FIP is 3.00 and he pitches 180 innings (60 runs allowed). You could see the fielder's projected +/- runs in 180 innings and then add or subtract it from 60. Obviously there's more to it since some pitchers get more groundballs, etc. so you'd have to look into it to be accurate.

MLB.com?

Whoever is watching the game data really. Not sure though.