While his main focus has been to help Otago win a title, he has also been popping across the Tasman to play for the Sydney Sixers in the Australian domestic twenty/20 tournament.
The 31-year-old impressed in his three games and picked up the crucial wicket of Owais Shah in the semifinal victory against the Hobart Hurricanes. The seven-run win secured the Sixers a spot in Saturday's final against the Perth Scorchers at the WACA.
McCullum would love to play in the final but he needs to be in Hamilton the following day for Otago's one-day game against Northern Districts and there is no question about his priorities.
"Unfortunately, I won't be able to head over, which is a bit of a shame," McCullum said.
"It is a bit disappointing to get so far with the team but I'm sure they will go well. Let's hope they win.
"But, first and foremost, I want to help win a trophy for Otago this year and we've got a fantastic opportunity to do that. We are sitting second on the [competition] table and, if we win these next two games, we will be in a good position to do that."
Otago (13 points) plays Central Districts (11) in Invercargill today and it is a crucial game for both sides.
With just three round-robin games remaining, a win for either side would be enough to book a place in the playoffs if Wellington (6) and Northern Districts (6) both lose their games against Canterbury (13) and Auckland (15) respectively.
"We're starting back at the one-dayers again and I don't think you can look further ahead than the next game and what we need to do as a team and as individuals," McCullum said.
Otago's twenty/20 campaign was probably best summed up as inconsistent but it did finish with a good win against Northern Districts. The team hopes to use that performance as a springboard.
"We weren't quite as consistent as we would have liked but we had a great performance in our last game. This is obviously a critical game for us. If we can win this game, it will put us right in the mix for the semifinals and finals.
"We've been involved in semifinals and finals before as a team in the past three or four years and have shown we can win those games."
While McCullum has been busy over the past few weeks flitting between two countries, he has enjoyed the experience.
"It was a great challenge and I've got a lot out of it.
"As an overseas pro, there is a bit of pressure on you to do things well, but I was pretty pleased with how I went. I would have liked to have scored a few more runs but when you are batting at No6, 7 or 8, you don't always get the opportunity.
"But to win every game I was involved with was pleasing."
"You are playing in front of crowds of 20,000-26,000 people as opposed to 2000, 3000 or 4000 people. They have a bigger group of players over there and a number of overseas players ... of high profile. So that adds to the intensity and the level of cricket that is being played. It was a great standard, but I don't think the HRV Cup is too far off what it is like over there."
Volts v Stags
Invercargill, today
• Otago: Aaron Redmond (captain), Neil Broom, Michael Bracewell, Craig Cumming, Darren Broom, Nathan McCullum, Jimmy Neesham, Derek de Boorder, Ian Butler, Neil Wagner, Nick Beard, James McMillan.
• Central Districts: Jamie How (captain), Carl Cachopa, Dane Cleaver or Kruger van Wyk, Michael Mason, Adam Milne, Tarun Nethula, Kieran Noema-Barnett, Jacob Oram, Dean Robinson, Mathew Sinclair, Bevan Small, Greg Todd.
