Even with soft conditions and preferred lies, none of the players in Sunday's final group at Colonial managed to break par.
Their struggles came in spite of the PGA Tour's highly unusual decision to institute lift, clean and place through the green, allowing players to take their ball in hand even in the rough.
Na got off to a hot start with birdies on his first two holes but didn't make another until the 18th. In between, he made three bogeys and a double.
Poulter, on the other hand, started off with a bogey, made the turn in even par, and closed with nine consecutive pars.
Hoffman traded three birdies for three bogeys.
An indication of their joint struggles, Poulter hit his second shot on the par-4 ninth in the pond guarding the front of the green and on the very next shot Na did the same.
Na and Poulter have both had their struggles this year when atop the leaderboard. Na made double bogey on 18 Saturday at the Players to forfeit his lead before a Sunday 71 left him out of the mix. Poulter entered the final round of the Honda Classic with a three-shot lead before losing a whopping five balls in the water during a Sunday-Monday finish.