"I'm very grateful. They've shown a bit of faith in me, so hopefully I can repay that when I get out on the field," he says. He was brought into camp early last month even when he was rehabbing, just to stay in touch with the systems.
The selectors have shown faith in Trainor because he has already shown bottle and talent on the big stage.
How many teenage wings make their provincial debut in a Ranfurly Shield challenge and look the part from the outset?
Trainor did just that on the wing when Waikato pinched the Shield from Hawke's Bay last October.
That followed some compelling form for the Waikato Juniors in the Jock Hobbs Memorial national Under 19 tournament in Taupo, where his speed and skill helped them to the final.
Close observers of the Auckland 1A competition will recall a classy fullback for St Peter's College who was the best goalkicker in the grade in 2014, winning him an NZ Schools berth.
New Zealand Under 20s assistant coach Craig Philpott refers to Trainor as "a special player," but jokingly quips he has completely forgotten about Trainor's Waikato debut on the night his Hawke's Bay side were divested of the Shield.
Trainor is one of 10 goalkickers, no less, among the backs, but he is potentially the best of the lot off the tee. In general, the squad is riddled with talent.
"We always back ourselves just to play. New Zealand sides are always expected to do well. The boys are in a good space at the moment," Trainor says.
Philpott knows some of his charges will make a name for themselves in this tournament. Some already have, with a clutch of Super Rugby players in the mix.
"There'll be some guys who aren't too well known, but I'm picking by the end of this, people in New Zealand will know who they are."
*New Zealand open their campaign on Wednesday morning (6.45am NZT) against Georgia.
