McCullum failed to fire as the Heat beat the Hobart Hurricanes in two practice matches on the Sunshine Coast at the weekend.
But he did smash 36 off 22 for Brisbane club Ipswich-Logan last week in his first innings since surgery.
Vettori said he was confident McCullum and Chris Lynn, another Heat star coming off an injury lay-off, will be key contributors despite interrupted preparations.
Lynn dislocated his shoulder in September during a fielding drill with the Australian side on tour in Sri Lanka.
"I think they know what to do to get themselves up speed pretty quickly," Vettori said. Winners of the BBL in 2012-13, the Heat have not qualified for the finals for the past three seasons, but Vettori is expecting that to change.
"It's a fresh start, the addition of Brendon will make a big difference - his leadership, his ability at the top of the order, and hopefully the way he plays can rub off on some of the less experienced guys," he said.
"There's high expectations of our batting order and with the bowlers we've got, we can scrap and find a way because there's some really good guys in that set- up."
The only Heat player unavailable for selection on Wednesday night is injured left-arm paceman Josh Lalor.