As opposed to the lapses made by Williams, Jags and Martina this season? oh and Rooney.. so many times in games he's played the ball backwards with out looking, giving it to the opposition.
I'm not talking about the risk from an in-game point of view, more the risk that it knocks their confidence and gets the crowd on their back.
Rooney is a seasoned pro, he's not going to let a mistake or the crowd change his game at this point in his career. Same for Williams, Jags and Martina.
What you don't want is an attacking fullback like Kenny coming on, screwing up and then playing within himself going forward.