At his best it'd be a difficult selection between Mullen and Matty Johns if they played in the same era.
All hypothetical, but imagine a pairing of Matty and Joey up against Mullen and Pearce. The Johns boys would more often than not get the points, but it would be an awesome spectacle. All four of them are game-breakers in their own right.
Just my opinion, but had he not been hampered by injury Mullen could have notched up around 300 games by now may very well be our current captain.
Unfortunately it'll always be a case of what could have been...