Tuipulotu's big chance came with Culum Retallick's knee injury at the start of the year, which had Kirwan scrambling for a replacement. However, it is the youngster, in tandem with veteran Tom Donnelly, who are the Blues' first choice locking pair now.
A knee injury of his own this season threatened to halt Tuipulotu's progress, but he proved again against the Waratahs' giant pack last weekend that he is a player with a big future. He was as sore as he has ever been following his collisions with Will Skelton and Kane Douglas, both of whom are 130kg-plus, but he emerged with his reputation enhanced.
"[Kirwan] is giving me game time to do what I do best and that's running with the ball," he said. "I think I provide good go-forward for us.
"Growing up I wasn't a big ball carrier. I did my core roles but didn't run with the ball much. It's something I enjoy - it's good for me."
The finesse and skill that Tuipulotu has added to his game has been made all the more dangerous by his size - another fairly recent development.
"I was always tall in my younger days, usually the tallest in the class but I was a skinny guy, real skinny," the former St Peter's College student said.
"I started putting on weight probably in my fifth form year when the 1st XV started giving out gym programmes and free gym memberships."
Tuipulotu is now aiming to put his full weight into tonight's challenge against the Reds at Eden Park. After dispatching the Sydney-based Waratahs last weekend, a victory over the inconsistent Queenslanders is well within the Blues' grasp.
One of the areas for improvement, however, is the lineout, which Tuipulotu conceded. Last weekend, the Blues' attack was halted in its tracks by poor execution in the set piece.
"Individuals must be clear what their roles are," he said. "During the week we look good but during the game ... it can be a bit of a shambles, but in saying that we are working really hard on it."
Kirwan said at the weekend he was keen to protect Tuipulotu because of his age and the fact he was consistently operating with such a disregard for his safety against bigger and more experienced players.
The man himself, though, doesn't see it as an issue. "I don't think I need a rest. I think when they look at me and Tom Donnelly and ask who's going to play the 80 minutes, I think they'll look at the young guy first. I'm not looking to be protected too much. It's not a big thing for me."