He enters with three advantages over most teammates: prior knowledge of the venue, regular net practice against their opponents' latest spin offering and a firm grasp of the New Zealand captaincy.
McCullum called the venue, Swalec Stadium, home when he played for Glamorgan in 2006. When it was known as Sophia Gardens, his two highlights included 160 in a first-class match against Leicestershire and 63 off 26 balls in a T20 match against Worcestershire.
"Cardiff brings back memories of good restaurants and golf courses. The ground's changed a bit since James [Franklin] and I were here in 2006 but it's nice to see some familiar faces. It's a beautiful place."
McCullum is the only New Zealander to have had consistent practice against Sri Lanka's latest off spin wunderkind, Sachithra Senanayake. The 28-year-old has only played 10 ODIs but his ability to disguise deliveries will be a focal point for the New Zealanders after he took nine wickets at 23.22 in this season's Indian Premier League. McCullum practised against him with the Kolkata Knight Riders.
"Satch is a different proposition altogether," McCullum says. "He is definitely one of the more mysterious spinners going around. He's got good variety and we can't give him a sniff or he'll expose any frailties to spin. I still hope we can play the Sri Lankan spinners with some freedom. Hopefully we've accumulated enough knowledge from various sources to be successful.
"Spin shapes as a key factor at this ground. With big square boundaries the spinners could have quite a say in matches but if they miss their targets it might be possible to hit them [to the shorter boundaries] straight."
Sri Lankan captain Angelo Mathews said spin is their priority after ODI success against New Zealand in November.
"On this pitch it also looks like spinners might come into play. It looks like it could slow as the game progresses."
McCullum is creating an excellent reputation as captain among overseas media who queue up to attend press conferences because of his willingness to respond frankly and in-depth.
However, he will see this match as a chance to back up his words and improve his ODI record, both against Sri Lanka and in tournament play.
Against Sri Lanka McCullum has never passed 50 in 17 ODI innings. His best was 47 not out in Dambulla just over 10 years ago. He averages 16.93 at a strike rate of 66 against them, compared to a career average of 30.98 at 90.
In 28 innings from three World Cups and three Champions Trophy tournaments McCullum has also never passed 50 against a top-eight nation.
He made 52 not out against Canada at the 2007 World Cup, along with a 101 against Canada and a 76 not out against Zimbabwe at the 2011 edition. Admittedly most of his innings have come batting down the order, where it is harder to make bigger scores.
McCullum says this tournament is the perfect format for the New Zealand team to excel.
"We only need two to three wins to make the semi-finals and it's played over a short period. That suits our style. I'll be disappointed if we don't make the semi-finals. If you get success you've earned it because they're all top teams. They have the format right."
Team naming delayed
New Zealand will not name a team until a late check on whether Daniel Vettori's Achilles tendon has improved enough to play.
The same applies to Grant Elliott's tight calf muscle. Elliott has donned a walking sock for the last couple of days.
If both are ruled out, New Zealand will likely opt for the same XI who played the Nottingham ODI against England.
If only Vettori is fit, Colin Munro could drop out with McCullum and Franklin shuffling up the order to create a vacancy at No.7.
