"He's running 01.08 [for the half marathon] - that's world class for an under-20 runner."
Sunday's race marked an 11-second improvement on the half marathon time Voss, who now lives in Reporoa, posted at the Rotorua marathon day last month.
Stevenson praised the young athlete's tireless drive.
"Michael ran two of these things inside a month, and he's only 18. He ran the local race here [in Rotorua] and ran out of his tree.
"He's got a phenomenal work ethic. I just say 'do this' and he does it. In the last year, he has trained extremely consistently."
Stevenson retired from teaching in 2014 but remains a well-known figure in the Rotorua athletics community.
Over the years he has coached a number of the city's notable athletes, including former under-19 New Zealand steeplechase champion Liam Walsh.
Stevenson began working with Voss last year, after the teenager asked for help in rectifying a haphazard training schedule.
"It took three months to sort him out," the coach said. "He had got himself all tangled up."
That seems hard to believe now. Under Stevenson's tutelage, Voss was soon keeping pace with the leading pack at national junior events.
He suffered a shin injury in an accident involving a rotary hoe at the end of last year - days later, at the New Zealand Secondary School championships in Wanganui, he shaved off half a minute from his best 3000m time.
Sunday's feat will have caused many in New Zealand athletics to sit up and take notice of Rotorua's latest running star.
