Scott Sattler said paul Whatiura was the most professional player he has seen, thats why the Wests Tigers went so hard after him.
A professional player would be someone who puts in 100%, makes little errors, gives away no penalties, misses few tackles, dosen't get injured and basically looks like they know what they are doing. Also be respected on and off the field
Steve Price, Hazem El Masri, Jason Smith and Steve Menzies all spring to mind.
But I'll throw one in who for me fits my criteria down to a tee:
Matt Sing