McMains was pleased with his side's abilities to produce points in the half-court late in the game.
"We just have to keep improving on recognising when maybe we don't have a numbers advantage, so we can slow down and execute our stuff. I think in the fourth quarter we showed a lot of maturity and growth to be able to get through that."
Airs forwards Jordan Ngatai (22 points and nine rebounds) and Aaron Bailey-Nowell (23 points, seven rebounds and five assists) dominated against a Rangers front-line missing Mika Vukona.
Eric Devendorf's 36 points was a bright spot for the hosts, who slid to 0-2 after losing a vastly contrasting game earlier in the week to the Wellington Saints.
The Saints took out that Thursday night opener 116-95 in a free-flowing offensive contest, before penciling in their status as one of the title contenders by sweeping aside the Hawke's Bay Hawks 89-74 on Sunday.
Wellington's premier challenger for the title are set to be the Southland Sharks, but their season started slowly, suffering a beatdown at the hands of a Giants side on a back-to-back and missing key point guard Jarrod Kenny.
The Sharks had won 16 straight games on their way to the title last season, and were installed as season favourites. However, they were missing Thomas Abercrombie and Duane Bailey, while Everard Bartlett and Alex Pledger landed in Southland just hours before the game.
As a result, Nelson - whose season had started poorly the night before with a 100-86 loss to the Canterbury Rams - came out of the blocks with a cohesive display against a muddled Southland unit, thrashing the hosts 106-80.
Four players scored 20 points for the Giants, with Breakers development player Finn Delany starring in an increased role, dropping 25 points to go with 13 rebounds.
OVERTIME
Many NBL players have had their name spelt wrong in programmes or media guides, but the Supercity Rangers went a step further.
Rangers forward Nick Barrow suffered the ignominy of having his name spelt wrong on the back of his jersey, becoming "Nick Burrows" to everyone in attendance.
Highlight of the Week
Sydney Kings and Wellington Saints swingman Dion Prewster with a crossover and then a one-handed finish.
NBL Ladder:
1. Wellington Saints 2-0
2. Canterbury Rams 1-0
3. Taranaki Mountain Airs 1-0
4. Nelson Giants 1-1
5. Southland Sharks 0-1
6. Hawke's Bay Hawks 0-1
7. Supercity Rangers 0-2