Despite playing just 50 minutes in a practice match a fortnight ago against Fremantle and then three-and-a-half quarters in an Eagles intraclub on Friday night, Longmuir says Naitanui is set to explode on Sunday at Patersons Stadium.
"The way he's leaping at the footy, he did a fair bit of centre bounce work in our scratch match last week and looked to have his leap there, so that's exciting," Longmuir said.
"Obviously his endurance won't be at full peak because he hasn't had the match fitness but we're hoping that his explosiveness is still there."
Simpson admitted on Perth radio on Monday night that he was unsure of what Naitanui was capable of and Longmuir was looking forward to seeing the new coach's reaction when his star ruckman gets up and going.
"Adam will be surprised with what Nic can bring to the side," Longmuir said.
"Looking at it from an opposition's point of view, as Simmo has looked at him in the past, sometimes you don't get the full perspective.
"It will be interesting to see what Adam's thoughts are after he watches him for the first half of the year because he's an exciting beast and he doesn't need a lot of possessions to influence the game so we're looking forward to getting him at full fitness."
Longmuir anticipated Naitanui would play a full game on Sunday but did suggest he could be subbed out late if the opportunity presented itself.
The task for the Eagles' match committee is to decide whether they opt for a third tall in Scott Lycett or Callum Sinclair to complement Dean Cox and Naitanui. Sinclair would need to be upgraded off the rookie list to play but has been in terrific form in the pre-season.
Exciting youngster Dom Sheed is in line to make his AFL debut on Sunday. Longmuir believes last year's under-18 Larke medallist will have an impact this year regardless of whether he plays this week or not.
"He'll be in the 27 names that are on the board that we have to go through," Longmuir said.
"If he doesn't get a go this week I expect him to play throughout the year.
"He's a mature-bodied kid who's got a good head on his shoulders. He's shown at under-18 level last year that he can dominate games so we're excited with what we've got."
Recruits Xavier Ellis and Elliot Yeo are all but guaranteed to play their first games for West Coast after strong pre-seasons.