His debut success came at the expense of Secret Agent, who was runner-up in the Gr.3 Phoenix Park 2YO Classic at New Plymouth at his next appearance.
Celtic Boy then finished fourth behind Role Model, a subsequent placegetter in the Gr.2 Swap Contractors Matamata Breeders' Stakes, with his rider later suspended for failing to ride the gelding out fully in the closing 100 metres.
"We're just going to take it step by step with him, there are so many things that can go wrong," Green said.
From the family of the two-time Gr.1 Australian Cup winner Vo Rogue, Celtic Class has yet to race on a rain-affected track but Green doesn't anticipate any problem.
"It was pretty wet the day he trialled at Paeroa and he ran third so I think he'll be okay," he said.
Among his Ruakaka rivals is a filly with a pedigree to back her claims for early success with Roger James' Fastnet Rock filly Miss Foxwood a royally-bred contender.
She is out of the dual Group One winner Foxwood, who won on debut as a two-year-old.