http://news.bbc.co.uk/sport1/hi/football/teams/w/watford/6183363.stm works out an aaverage - i hope they do this in future games
You can already do this on skysports.com with Premiership games. After the game the games, go to their match report then click on 'player ratings'. They keep a running tally of the ratings over the season. http://home.skysports.com/squadlist.aspx?clid=57&cpid=8