Funaki's a great fighter - no doubt, but much like many Pancrase fighters he really wasn't all that great when punches on the ground were allowed. Years of focusing and training a certain way can do that. When they allowed the more open MMA rules in Pancrase you can see the 'fish out of water' situation a few times. It's not quite like a jacketed BJJ champ taking off the gi and going NHB for the first time, but you can see a lot of floundering and people raining shots in those early bouts. Funaki's game from his back was solid early, but with striked involved he was only average. Years of taking slaps to the ears don't make for a long career either...especially when you fight every month for 4-5 years.
With ALL of that said, Funaki is still one of the best there has ever been at old shoot-style rules and it's too bad he didn't focus on the more open MMA rules earlier in his career. IMO he's EASILY the best opponent Rickson faced. Nakai is more talented, but when you're half-blind and outweighed by 30+ lbs. it's tough to do much...and I think he seemed to get really good AFTER that fight. Takada is probably next, along with Duarte, Zulu, or Yamamoto.