 Sabermetrician Bill James, too, performed research into CERA, finding that while it is possible that catchers may have a significant effect on a pitching staff, there is too much yearly variation in CERA for it to be a reliable indicator of ability.James used simulations of catchers with assigned defensive values to directly compare CERAs, which influenced Woolner to perform similar simulations but instead using weighted events to calculate pitchers' runs per plate appearance.Through this, Woolner concluded that even if catchers do have an effect on pitchers' abilities to prevent runs, it is undetectable and thus has no practical usage.