McCullum has been sidelined for the past month with a muscle strain and has been added to the side which lost to Northern Districts by 19 runs in Invercargill on December 20.
The explosive middle order batsman and economical off-spin bowler is a key member of the Otago side and his inclusion strengthens the line-up.
"We're delighted to have him back," Hesson said.
"He's a good middle order batsman and a more than decent bowler.
And he lifts the side in the field as well."
McCullum has played 75 one-day matches for Otago.
He has scored 974 runs at an average of 19.87 and taken 64 wickets at 37.92.
It is a useful rather than impressive record but in the past two season's McCullum has started to deliver on his potential.
Last summer he scored 205 runs at 29.28 and bowled a lot of overs for his nine wickets.
While he averaged close to 40 with the ball his economy rate of 3.91 was exceptional.
But it was in the Volts' successful twenty/20 campaign where he underlined his value to the side.
With a combination of innovation and power McCullum scored 165 runs at 41.25 and claimed eight wickets at 15.50.
He was also the most frugal of the bowlers, going for less than seven runs per over.
Anything under eight is considered pretty good in twenty/20.
In McCullum's absence Otago has produced mixed results.
It opened its campaign with a win over Wellington but has lost its last two matches and after three matches is in fifth place.
The one-day format has changed this year, with the round-robin phase cut from 10 to eight games, and the play-off series has been expanded to include four, rather than three, teams.
Otago will need to be in the top four at the end of the round robin to give itself the opportunity to extend its impressive one-day record.
The Volts won the title in 2007-08 and have played in the last three finals.
"Obviously, with the shortened competition, these next couple of games are important.
It is a big two games for us," Hesson said.
Otago plays Central today and Canterbury in Timaru on New Year's Eve before the competition goes into a month-long hiatus during the twenty/20 tournament.
It has been an odd one-day tournament, with games tacked on the end of Plunket Shield matches, pausing for the razzmatazz of the twenty/20 and resuming again in February.
It has not attracted the profile it has had in the past.
"It gets hard to lift the profile of all the competitions when you have three you have to prioritise.
Commercially, they [New Zealand Cricket] have certainly prioritised the twenty/20.
But the one-dayers are still a massive competition for us.
We've got some good history and we want to keep doing well," he said.
Central Districts is in third place, with two wins from four matches, and will be riding high after a superb run chase against Northern Districts last week.
Northern scored 300 for five but Central overhauled the total with some unbelievable hitting from Graham Napier.
The English professional clubbed seven fours and five sixes on his way to an unbeaten 73 off just 27 deliveries.
Former Otago all-rounder Kieran Noema-Barnett also chipped in with a hard-hit 45 and the in-form Peter Ingram anchored the top of the innings with a patient 59.
Experienced seamers Ewen Thompson and Michael Mason have been in good rhythm, and Black Caps all-rounder Jacob Oram remains a threat.
For Otago, Neil Broom and the skipper Craig Cumming pose the biggest danger to Central's attack, with Neil Wagner and Pakistan bowling all-rounder Yasir Arafat spearheading an attack which includes Black Cap Ian Butler and experienced campaigner Warren McSkimming.
