Back in the mid-1990s, Penrith legend Royce Simmons had a quiet word to the club's reserve-grade captain, Brad Arthur, explaining that his lack of size and pace meant he was unlikely to ever play first grade.

But Simmons told Arthur he had enough nous to potentially earn a quid as a captain-coach in the bush.

Arthur duly applied for a vacant position at Group 16 club Batemans Bay and, after reportedly telling a fib about his age, the 21-year-old was handed the reins.

The team included an 18-year-old rookie named Adam O'Brien, who was blown away by the level of professionalism Arthur introduced the Tigers.

"He was ahead of his time," O'Brien said.

"He brought in stats, and video, and just the stuff we started doing at training, you could tell he was born to be a coach."

After two years at Batemans Bay, Arthur headed to Cairns and steered the Brothers club to four premierships and six grand finals in eight years.

O'Brien waited to win a premiership with his home town, then followed Arthur north and also to Melbourne, where the former had been hired to coach the Storm's inaugural under-20 team.

After a brief stint as Manly assistant coach, Arthur took charge at Parramatta in 2013, and on Sunday he and O'Brien will go head to head for the first time when the Knights host the Eels at McDonald Jones Stadium.

"I've lived with him, I'm godfather to his daughter Charlotte, my wife Sharyn and his wife Michelle are really close," O'Brien told the Newcastle Herald.

"He's played a huge part in where I am today.

"Number one he gave me a chance. He was the initial one and then [Storm coach] Craig Bellamy helped me continue on my journey."

O'Brien said he still speaks to Arthur regularly and was actually in touch with him on Thursday, to help organise tickets to Sunday's game and also the scrimmage for fringe first-graders.

"It's like my relationship with Craig," O'Brien said. "We don't talk too much about the actual game. It's more about families and stuff like that."

The pair will share a post-match beer, but for 80 minutes on Sunday they'll be focused on the job at hand.

"We're both really competitive," O'Brien said.

"But it's the same every week. We just want to prepare our teams the best we can, and the players will sort it out on the field."

Arthur has guided the Eels to top spot on the ladder with seven wins from eight games this season, but the Knights are hoping to reproduce the resilience they showed in last week's 14-12 triumph at Brookvale.

"We've been a little bit inconsistent," O'Brien said. "Now it's about maintaining that resolve that we had last week and looking to improve in a couple of areas."