McCullum, who has long battled a bad back, damaged a disc diving for a ball on the boundary during the second match in Christchurch on Monday which the hosts won comfortably to take a 2-0 lead in the five-match series.
“He’s still pretty sore,” Hesson told local media on Wednesday.
“It’s unlikely he’ll play but he’s still a chance.
“Normally we talk about 24 to 48 hours (for recovery). It’s probably closer to 48 than 24. He’s certainly improving but unless he’s good to go, we won’t risk him.
“He’s certainly one of those guys that if there’s a chance he can play he’d like to.”
Batsman Kane Williamson and fast bowler Adam Milne are in line for selection after recovering from injuries, however.
Williamson hurt his knee fielding during the second test against Sri Lanka in Hamilton but proved his fitness in a full training session.
“Kane’s great. He was keen to play the last one but he was still pretty sore. He’s trained well today and recovered well,” said Hesson.
New Zealand will also play Sri Lanka in Twenty20 matches on January 7 in Mt Maunganui and Auckland on January 10 as part of their preparations for the World T20 in India.
All-rounder Corey Anderson has been named in the T20 squad captained by Williamson and is set to make his return from a prolonged back injury which has kept him sidelined since the tour of England in May.
Anderson will only bat during the series as he eases back into international cricket.
“We’ve got a plan in place for when we hope to have Corey back bowling,” Hesson said.
“He’s getting closer, but we’ll be taking a precautionary approach.
“We’ve seen how dynamic a batsman he is and can threaten any bowling attack in the world. It’ll be great to have him back in the mix.”
All-rounder Grant Elliott, who struck the winning six off South Africa paceman Dale Steyn to guide New Zealand into their first World Cup final in March, has also been named in the squad after recovering from a fractured wrist sustained in November.
New Zealand T20 squad:
Kane Williamson (captain), Corey Anderson, Trent Boult, Grant Elliott, Martin Guptill, Mitchell McClenaghan, Adam Milne, Colin Munro, Luke Ronchi, Mitchell Santner, Ish Sodhi, Tim Southee, Ross Taylor.