"He was one of the better tacklers to come through the club in a long time," he said.
"I'm actually surprised it has taken as long as it has [for him to be picked]. We all knew he was quality."
The loose forward has filled out since his high school days to a healthy 106kg and will start tonight at No8.
Three injuries in the Chiefs No8 jersey have seen him given the chance to start tonight, with Ross Filipo, Fritz Lee and Nick Crosswell all currently sidelined by injury.
His first Super Rugby start will be against a strong Rebels forward pack led by their captain, and opposing No8, Scott Higginbotham.
However, McMillan said if his days at Whaka were anything to go by he shouldn't have a problem.
"[When he was at Whaka] he was the kind of guy you'd look at and think he wouldn't be very aggressive or have a very big physical impact," he said.
"But he expressed himself on the field. In terms of his defence he was very physical and a really good tackler."
Vant Leven's first appearance at Super Rugby level was made off the bench for the Chiefs in 2011, the same year he made three appearances off the bench for the club.
However, the Waikato ITM Cup player was not re-signed by the Chiefs last year and had to wait until this year to be re-selected for the wider Chiefs squad.
Fellow Rotorua Boys' High School old boy Liam Messam will also start for the Chiefs tonight. Vant Leven made 48 appearances for Whakarewarewa before leaving to Hamilton's Fraser-Tech in 2010, to give himself a better chance of playing ITM Cup rugby. Vant Leven could not be reached yesterday for comment.