Former St George Illawarra Dragons coach Paul McGregor said it was a "huge honour" to join the NSW Blues coaching staff in 2022.
The man more commonly known Mary will replace another former Dragons and NSW player Craig Fitzgibbon as an assistant coach to Brad Fittler. Fitzgibbon stood down from the role to coach Cronulla next season.
"It's a huge honour, after representing the Blues right through the 90s as a player and now to be on the coaching staff ... I have a lot of gratitude and appreciation around that," said McGregor, who parted ways with the Dragons during the 2020 season after coaching them for 151 games.
"I have a lot of passion for the game and perseverance as well. I believe I have gained 'Freddy's' trust and earned his loyalty over time. In his first year coaching the Blues  he took a lot of my [Dragons] players into the series and they won.
"It's important to me to influence his vision on the team and I will do that with purpose."
Fittler said it was "outstanding" to link back up up with his former Origin roommate.
"Obviously it is disappointing to lose Craig Fitzgibbon, who made such a valuable contribution to our group over the past three years, but to replace him with someone of the calibre and experience of Paul McGregor is outstanding," Fittler said.
"I have been fortunate to have played with Mary and roomed with him during the early 90s playing State of Origin and he will fit perfectly within the culture of our group, as well as adding immense value in what he can bring as an astute coach.
"He is really passionate about the game and NSW."