I'm going to rank them in order based simply on what their output in the ruck (as in I don't care if they can rest fwd and kick goals) in 2010 alone would be IMO if they played first ruck...
Cox
Sandilands
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if your going to discount around the ground then sandilands is obviously number 1, he wins the most taps, the most to advantage and the most clearances of any ruckman.