"We lacked the batsmanship required through the middle," Hesson said.
"Certainly it was a bit more like an old school one-dayer, a bit more in it for everybody and it certainly required a different skill set than often required."
Hesson pointed out it was a difficult pitch for batsmen to get started on. Williamson was the only player in the match to reach 50.
"There was some poor decision making, others (showed) a bit of lack of execution. It just required a bit of batsmanship through the middle to bat with Kane and we didn't get it until Mitch (Santner) came in and did superbly."
Those in the firing line include out-of-sorts Henry Nicholls, newcomer Mark Chapman and allrounder Colin de Grandhomme, who played a dreadful shot, holing out to long on.
But Hesson insisted New Zealand can still win the series, which resumes in Dunedin on Wednesday.
"Of course we can. We've had two pretty close games and it's been a great series so far."
Hesson labelled Williamson's 11th ODI ton as "probably the best he's played in 12 months, I reckon, in terms of the way he stuck to his game plan from ball one."
Senior batsman Ross Taylor is expected to return to the side for Dunedin, after injuring a quad muscle in the game two loss at Mount Maunganui.
"He's making good progress so we're hopeful," Hesson said.
Chapman is staying with the squad as cover in case Taylor has a setback.
