Mr Bartley told Morning Report the 22-year-old McDonald had come a long way, and was the favourite for the $6.4 million race at Flemington which starts at 5pm today (New Zealand time).
The last New Zealand jockey to win was Jimmy Cassidy on Might and Power in 1997.
"[McDonald's] a lovely rider, [he has] a good feel for horses over distance," Mr Bartley.
New Zealand horses and jockeys had underpinned the race for years, with just one Australian horse in this year's race, he said.