Millar has joined an exclusive group of players to transfer between the F3 derby rivals after signing a two-year deal with Newcastle.

As the likes of Roy O'Donovan, Andrew Hoole, Ben Kennedy and even Jets chief executive Lawrie McKinna will testify, fans tend to show no mercy to those who cross the great divide.

"I have nothing but good things to say about the Mariners," Millar said.

"They gave me my chance, plucked me from the [Victorian] NPL. We had a really good bunch of boys. Results didn't go as we would like, but I have no bad things to say about Mariners."

Millar said a bit of stick from the crowd is "to be expected", but having played in three F3 derbies last season, he felt the atmosphere brought out the best in both teams.

"They're the games you look forward to playing in," he said. "A lot of people in the stands and a good rivalry, so I'm looking forward to that."

Millar grew up in Langwarrin, outside of Melbourne, and made his A-League debut for Melbourne City as a 19-year-old. After four games for City, he spent two seasons with South Melbourne before joining the Mariners last season.

His pace at right back attracted the attention of Jets coach Ernie Merrick, who identified him as the ideal replacement for Wanderers-bound Daniel Georgievski.

"Ernie has been really encouraging with me as a fullback, trying to get forward and hurt teams going forward," Millar said.

"But we also want to have a good tight back four, back six, and defend as a full team. So I'm really enjoying training so far."