The 21-year-old, regarded as the leading young playmaker in the game, has been backed by coach Kristian Woolf to be an even better player in the Pacific Cup this year than he was last season when he announced himself as a rare talent.
Katoa will play against Samoa at Suncorp Stadium on Sunday with a remarkable points record under his belt.
Tonga's Test records are sketchy, but NRL statistician David Middleton has Katoa out in front, based on official Tests dating back to 1995.
Katoa has 67 points in his nine Tests from two tries, 29 goals and a field goal.
"I have Isaiya out in front of Siosiua Taukeiaho on 60 points, from two tries and 26 goals," Middleton told AAP.
Katoa is on the cusp of streaking ahead of the rest of the field.
"He will be around for a while too. He is coming up to 10 Tests and he is only 21," Middleton said.
Katoa was a fan favourite when thousands of Tongans turned out to watch the side train at Logan Brothers on Thursday.
Tonga co-captain Jason Taumalolo said the team was in good hands with Katoa steering the ship.
As a teenager Katoa excelled for the national team while still a student.
"We knew how mature he was when he was doing school exams at the 2022 World Cup," Taumalolo said.
"To go from that to where he is now speaks volumes for what kind of player Izzy is.
"The feature of Izzy this year, and looking ahead, is for a young half to be so dominant. You don't see many halves come through and play the way he does.
"I am sure the boys are confident going into this game having Izzy alongside them steering the ship.
"Whatever Izzy says, goes."
Woolf sat down with Katoa after the Dolphins' season finished and was impressed with his desire to shine in the Pacific Cup.
The duo talked footy in clubland, where Katoa completed his best season in the NRL, but the coach was stunned by his preparation for the Tests.
"I know he's really hungry to get into this camp," Woolf said.
"We watched a little bit of video and had a bit of a chat about how we want to play.
"You could just tell in the way he spoke and how engaged he was that he'd been thinking about it well before I had, so he's ready to go.
"I think last year's (Pacific Cup) series gave him a lot of confidence in what he can do at such a high level against Australia in two games and against the Kiwis as well.
"I just know that he's coming in so much more confident, so better prepared.
"He's going to be a better player again, and I'm sure he'll get more confidence out of this series as well."
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