Ronan O'Gara will join the Crusaders in the New Year after agreeing terms for a one-year deal to work as an assistant coach with the Super Rugby side.

Earlier this month Scott Robertson met Ronan O'Gara in a Dublin restaurant and asked the Irishman if he fancied moving from Paris to Christchurch.

Crusaders head coach Robertson needed a new assistant backs coach and ex-Ireland first five-eighth O'Gara, who had made 128 appearances for his country between 2000-2013, was at the top of his list.

Not convinced anyone in New Zealand had the credentials to replace the departed Leon MacDonald, Robertson arranged a meeting with O'Gara when he assisted Robbie Deans with the Barbarians in the northern hemisphere.

Top o' the mornin' to ya! We have some exciting news to start your day, to be sure - @RonanOGara10 is our new Backs Coach! Read more at https://t.co/tmWAOQS6CB #crusadeon pic.twitter.com/tjPcY6WZvH — BNZ Crusaders (@crusadersrugby) November 22, 2017

"I was fortunate to catch-up with him for lunch in Ireland before the Springboks test match and I just couldn't believe how much of a superstar he is over there," Robertson said. "I was blown away by how much he is held in such high regard.

READ MORE: Ireland great joins Crusaders

"The biggest thing that sold it for me was when I asked 'why would you like to be a Crusader? And he told me it was the holy grail'. That was enough for me."

O'Gara has signed a one-year deal with the Crusaders, having negotiated an exit from glamour French club Racing Metro as its defence coach. He will arrive in the New Year.

NZ Rugby didn't stand in the Super Rugby champions' way.

"They (NZ Rugby) were consulted throughout the process," Robertson noted. "It goes both ways, we can all learn from this and they were happy with it."

While Robertson and another assistant backs coach, Brad Mooar, are contracted to NZ Rugby, O'Gara's deal is directly with the Crusaders.

Often coaches from New Zealand fly north to link with clubs in Europe and Japan. It's not often that it happens in reverse. Robertson, though, has done this before.

When he started as Canterbury head coach in 2013 he convinced former Manawatu playmaker Jason Holland to relocate from Munster - the same club O'Gara played for in Ireland - to Christchurch.

That plan worked well enough for Canterbury to win a title, resulting in Holland being poached by the Hurricanes.

"Firstly I looked locally but the experience I wanted wasn't in New Zealand, so I broadened my thinking," Robertson said in reference to O'Gara. "We we looking for someone who has experienced rugby at the highest level and performed in pressure situations.

"'Rog' (O'Gara) has done that as a player for different teams, and also as a coach. So I just thought I would sound him out and give him a call."

O'Gara initially started working for Racing Metro as a kicking and skills coach after he retired in mid-2013. Robertson wouldn't name his contacts, but confirmed he had spoken to a variety of people when doing his due diligence.

The Crusaders players also endorsed the idea of O'Gara being recruited, Robertson stated: "We have got a lot of All Blacks players who have played a lot of rugby, in long campaigns. Someone with a fresh voice and new accent and a different perspective, is something that will be fresh for all of us.

"He is the real deal."

Mooar will retain the portfolio that proved successful for the Crusaders this year. Among other things he will continue to work with the halfbacks, first-fives and No 12s and be charged with shaping the attack plays and game plans, while O'Gara will take care of the rest of the backline, the counterattack, do a lot of the kicking plans and assist Robertson with the defence.

"I know he (O'Gara) is good on and off the field," Robertson noted. "He loves the Guinness, but I know he loves footy and to work hard. So it is a good balance for us."