"I'm really staggered I've still got him. I mean, he's done the same for me last year as well to win a world series," the long-time national sevens coach said.
"He's a magnificent footballer. I think he's about 110kgs, ran a 14 in a beep test, which is tremendous for a young Tongan boy who is 23. I'm probably just staggered that he can't make a [Super Rugby] wider training group.
"It's just his ability to beat players one on one. Just a great fend and he's really quick and for someone so young he can offer so much and on the sevens field that's his game at the moment. But he can play equally as well in 15s and I've seen him. So, again, not wanted by the Super Rugby teams, but I'll certainly have him any time he wants to play this game for New Zealand."
Halai's importance will be magnified during the remaining tournaments on the series with Gear unavailable as the World Cup-winner returns to Super Rugby duties with the Highlanders.
Tietjens indicated Taranaki's Waisake Naholo would replace Gear in the 12-strong squad for next weekend's fifth leg of the nine-tournament series in Las Vegas in the United States.
Another player Tietjens will have to replace is back Toby Arnold, who injured his knee in the opening pool game against Scotland and could be out for up to nine months.
Arnold's spot was filled admirably by debutant Mark Jackman during the rest of the weekend and he showed good judgement in defence and is a handy runner with the ball.
There was plenty of hype around Wellington youngster Ardie Savea heading in to the tournament, but the 18-year-old younger brother of Hurricanes wing Julian Savea rarely featured.
New Zealand's road to the final was hardly ideal as they had to come from behind in their quarter and semifinal victories over France (22-7) and England (17-12) respectively.
Fiji on the other hand, took an unconventional route to the cup final after they only qualified second in Pool C after they were upset by Tonga in the group stages.
The perennial powerhouses of the sevens game overcame the impressive South Africa 21-5 in the quarter-finals and dispatched Samoa 28-5 in their final-four encounter.
Fiji, who were playing in their seventh final in Wellington, were always going to find the slippery conditions tough and never got out of first gear.
The Pacific Island nation, who last won the tournament in 2010 when they beat Samoa 19-14, couldn't keep up with the slick Kiwis who defended well.
In the minor finals, Scotland beat the Cook Islands 19-17 to claim the shield, while crowd favourites Kenya downed Australia 12-7 in the bowl final.
After showing strong form during the pool rounds, South Africa knocked over Tonga 24-0 in the plate final.
Despite having the fans on their side, Samoa were unable to get past England in the battle for third place and went down 21-12.
Cup final: New Zealand 24 (Frank Halai 2, DJ Forbes, Tomasi Cama tries; Cama 2 con) Fiji 7 (Waisea Nayacavelu try; Metuisela Talebula con) HT: 24-0
