That has left O'Connor, 22, Raglan's Billy Stairmand and 35-year-old Gisborne veteran Chris Malone, who won the open men's division in 1998, to fight out a diluted men's final, with the rules not allowing a fourth surfer to take Hewitt's place.
The situation hasn't pleased everyone but O'Connor said Hewitt's decision was understandable.
"It's going to be weird and probably a bit of a bummer for the spectators that it's a three-man final but apparently the rules say they (Surfing New Zealand) can't go back because Matt's already beaten 90 per cent of the guys.
"Some people are saying it's unfair on the other competitors who've missed out but Matt's managed to beat everyone on his way to the final and it's a pretty unfortunate situation. Matty won here three years ago and has had a good build-up to the pro junior ... (and) at least one Mountie got through."
O'Connor blitzed the second semifinal in small 1m surf to eliminate defending champion Jay Quinn. He's looked sharp all week and doesn't see that changing today.
Stairmand, ranked 79th in the world, is being talked up as the firm favourite for the final but O'Connor has promised he won't get an easy ride.
"I'm stoked right now and couldn't be happier but as soon as I made the quarters, which is the furthest I've ever got, I've re-set my sights. I've dreamed of a national title since I was a kid competing, seeing Maz Quinn and those guys all win, and it (trophy) is something I want to grab the handles of and tick off the list.
"I've put myself in the spot but there's one more heat to get through. I won't be nervous, more excited and amped up I suppose."
O'Connor has based himself at Stairmand's house in Raglan for the past two months, with the pair out surfing every day at Manu and Whale bays. His dream conditions today would be 1.5m swell fanned by an offshore breeze. "Billy's a good mate and the final will feel just like another free surf. Bugsy (Malone) is another good mate and the final will come down to whoever gets waves on the day. I'm confident how I'm surfing and came here with high expectations."
The open women's division final takes on an old versus new look, with home surfer Mischa Davis and Thandi Durham (Taranaki) taking on 16-year-olds Ella Williams (Whangamata) and Jayda Martin-Fitzharris (Gisborne).