Neurosurgeons temporarily removed a large chunk on the left side of the youngster's skull.
"When I woke up I had no idea what had happened," Tusi explained. "I couldn't move anything on my right hand side and I had 48 stitches in my head.
"The first thing I thought about was how I was going to get through my school exams and how I could get back playing rugby."
Surgeons told Tusi's distraught father Faamai Toni Eti it was touch and go whether his boy would live.
"I knew he would be okay afterwards when a doctor asked him what was going on in the world, and Tusi replied 'the Olympics'," he said.
The bright student, from Massey, wants to become a rugby professional.
"Tusi had been on our radar before the surgery and we are thrilled he has recovered and back playing so well," Shane King, schools' convenor for the Blues, said.
Avondale College rugby coach Mike Perez said it was nerve-wracking when Tusi, a school prefect, played his first competitive match just six months after the scare.