"I really wanted to win this one against the world champion. I am a big old turtle but I got there in the end," Whitlock said.
"The darts felt great … I can't wait for another good night."
Whitlock will meet Raymond van Barneveld in the semifinals, after the Dutchman dispatched Kiwi Mark McGrath in short order.
After upsetting fourth-seed Michael Smith in the opening round, McGrath wasn't able to match it with van Barneveld who took the match 10-4.
Fellow Dutchman and current world No 1 Michael van Gerwen had an equally impressive run against world matchplay champion Gary Anderson, also claiming a 10-4 win.
Van Gerwen has looked in sharp form since arriving in Auckland, looking to make amends for a poor performance in Shanghai in his most recent tournament. He will face another crowd favourite in 'Snakebite' Peter Wright, who beat 2017 Auckland champion Kyle Anderson 10-3.
Wright, who was eliminated in the first round of last year's competition, signalled his intentions to leave New Zealand with the trophy before the event, and his form has backed up his hopes. However, he'll have to go through an in-form Van Gerwen in what could be the match of the tournament.
- Additional reporting by Phil Dillon