He scored the second of the Blues' first-half goals with a trademark finish.
After Nathan Farey had made it 1-0 with a superb first-time finish on a cut back to the penalty spot, McNab controlled a perfectly waited floating ball with his touch before swiftly depositing it into the top right-hand corner.
The game failed to reach great heights after that, with the competition leaders likely having to guard against any letdown without their key striker.
"We've talked about it for the last two or three weeks and we knew it was always going to happen," said Lowry. "It's always going to be difficult when you lose one of your stars. It's got to come from within the squad.
"Everyone was playing with the handbrake on today, especially in the second half.
"I've built the team around Jack McNab. I've always said since I've been here I've only had one centre forward."
A glimpse of life without McNab produced some chances but no goals down the stretch, and the team may have to adapt its playing style without a proven target man up front.
Lowry said the side would use Saturday's match against struggling Claudelands to tinker with combinations ahead of Monday's Chatham Cup match away against Lynn Avon.
Tauranga City United AFC 2 (Nathan Farey, Jack McNab) Lynn Avon 0
