McNamara is a confidant of Burgess and has been with him through every big decision in his career since the pair met when the player was a teenager at Bradford.

He says Burgess' decision to join union before next year's World Cup on English soil could earn him national recognition.

"Sam's more famous in Australia than he would be in England," McNamara said.

"In the north of England where the rugby league heartland is, he's up there with the top sportspeople. But in other parts of the country he'd be relatively unknown at this stage. He could walk around London, he could walk around most of the cities in the country and not be recognised.

"But that's all about to change for him. His efforts in the World Cup will certainly make him a national figure if he's successful at it. That will open up a lot of opportunities for him further on in his life."

While McNamara said he was shocked by Burgess's decision to abandon the 13-man game, he said in hindsight it was no surprise he came to such a quick decision knowing how much he craves a challenge.

"It was a complete shock at that stage," McNamara said.

"It wouldn't have surprised me if it was two, three or four years down the line. Sam's a bloke who does make quick and strong decisions and I think at some stage in his career he would have certainly loved a different challenge.

"But the timing of it, knowing how well he was going in Australia and how much he loved living in Australia, it did come as a shock. But when you sit down and look at what's ahead for the England rugby union team this year, it's not a shock reflecting back. Sam loves the challenge more than anything and that's why he's doing it."

McNamara, the Roosters assistant coach, has a good relationship with the English rugby union coach Stuart Lancaster and his assistant Andy Farrell.

He said the English rugby union had targeted several English league players with the World Cup in mind.

"The England rugby union are a very powerful organisation and have been trying to build towards winning a World Cup," he said.

"Obviously 2015 being on English soil, it's a huge event for everyone involved. A lot of our players have been on their radar and a lot of them have [been] spoken to. But with Sam being in the NRL and the added financial benefits he can get in Australia, it came as a surprise they got him so quickly."

McNamara knew Sam's father Mark before he passed away, saying he would proud of what all four of his sons have achieved.

"Mark was around the scene supporting the kids all the time. He became quite seriously ill pretty quickly, but my overriding memory is his effort to get out there and support the boys right through the end," McNamara said.

"Seeing all four of his boys playing in a foreign competition, which is the elite rugby league competition in the world, with at least three of them involved in a grand final, that's something he'll be looking down on them with great pride. It's an incredible feat and I'm sure everybody involved is proud of them."