This just in from WIS:
"After further investigation the ratings used on the special teams is the average of every player at the position. This way it will get a general cross section of your team's depth.
For punts that is broken up into the Line Blocking, Line pressure, Return Blocking, return execution, return speed, return defense and return tackling.
The Speed determined in the fair catch uses defensive backs and linebackers, not WR. Sorry for the original misinformation."
So, DBs and LBs, not WRs.