One of the reasons the Red Sox traded Nomar in 2004 was that they determined he had significantly lost fielding range after his injury. At first they only suspected this by watching the games, then they hired some people to track Nomar on a play by play basis, and this confirmed their suspicions.
The outcome is well known, they traded for Cabrera, Cabrera played a great SS and they won the WS.
A simple and well known example of the value of metrics beyond fielding %.