Even if we had such a person, I would imagine that would make him good enough to fit into the starting 21. Also, say Jamar goes down injured and we have Bennell as our substitute, we're obviously not obligated to play him in the ruck. We would most likely switch things up so that Newton/Spencer/Martin goes into the ruck semi full-time, causing some others to change their roles, which would likely put Bennell into the position he would have normally played anyway. Frawley injured: Frawley subbed off, Garland switched to Frawley's spot, Rivers switched to Garland's spot, Bennell subbed on and put into Bruce's spot, etc. Thus, versatility is not necessarily the key to being a good substitute, although versatility within the team is still important.