A ringing endorsement from Alex McKinnon helped convince NSW coach Brad Fittler that Jack de Belin was the type of player he wanted in his new look Blues team for this year's State of Origin series.

De Belin, who will again start at lock in Origin III at Suncorp Stadium on Wednesday night, grew up playing alongside McKinnon at school and for St George Illawarra's under 20s team before the pair made the transition to NRL level at the Dragons in 2011.

They remain close mates and de Belin has little doubt McKinnon would be playing alongside him in the NSW forward pack if his career hadn't been cut short four years ago by a spinal injury which left him a quadriplegic after a tackle in a match for Newcastle against Melbourne.

Now awaiting the birth of his first child with wife Teigan later this year, McKinnon has remained involved with rugby league through various roles with the NRL, Knights and the media, and is considered an astute analyst of the game.

Fittler revealed he regularly used McKinnon as a sounding board and discussed the selection of de Belin with him before choosing the St George Illawarra backrower to start at lock ahead of Test forward Jake Trbojevic.

"I talk to Alex McKinnon a fair bit about footy and he has always had a high opinion of Jack," Fittler told NRL.com. "He said he is tough, he works hard and he does all the stuff coaches want to hear.

"Alex has always had a big rap on him, and he has most probably been on the cusp for a while, but he sat behind Trent Merrin for a few years at the Dragons so he has had to be patient. I think he is now starting to reach his potential."

De Belin attended McKinnon's wedding last October and said his former teammate had been an inspiration to him from the day they started boarding together at St Gregory's College, Campbelltown.

"We have had a fair journey together, we always keep in contact and whenever we get a chance to catch up we do," de Belin said.

"Footy was his life and he was always going to make it. As soon as I went to St Greg's, I could see he was such a talent and I haven't seen many better in terms of mindset and attitude. He was such an unreal trainer and player.

"He was destined for greatness and it was tragically cut short, but when one door closes another one opens, and whatever happens with Macca he always makes the most of his opportunities so you will never see him down and defeated "

What has impressed Fittler and Blues performance coach Hayden Knowles about de Belin is his work ethic and attention to detail in preparing himself for games.

According to Knowles, de Belin is usually the first NSW player in the gym and the last to leave.

"It's like it is just his thing; he has to be the last to leave," Knowles said. "We were at the gym the other day and all the boys walked over to the beach afterwards, but it was like he deliberately waited for everyone to leave, just to do one extra set.

"It is very impressive and I will tell any young kids who come in to first grade that that is why Jack de Belin is here, because of those qualities. Those little things off the field usually show on the field. When everyone is tired and there is one little job to do, it is usually him.

"He is the guy putting the kick pressure on when everyone else's arse is hanging out or he is the one who is first to dive on a loose ball. Those are the little things I look for in training and I have seen it in him in bucket loads."

Blues arrive in enemy territory

Fittler also spoke to St George Illawarra coach Paul McGregor about de Belin, as well as the other three Dragons forwards in the NSW squad, and attended a training session at WIN Stadium.

"He is a guy who just gets everything out of himself. It's no surprise he looks the way he does and he plays the way he does," Fittler said.

"I have been looking at him for a couple of years, I have been a big fan. He got a bit injured last year but this year is his time. He has obviously found a bit of confidence, he is ball playing a bit more and he gives his team a lot more. I just put it down to age sometimes."

After being 18th man for the Blues during last year's Holden State of Origin series, de Belin said he also felt more comfortable this year in a team boasting 11 debutants for the series opener at the MCG.

Cronulla prop Matt Prior made his debut in Origin II and St George Illawarra second rower Tariq Sims will replace him on the interchange in Wednesday night's series finale.

"When I was in the camp last year there were players who had been there for a few years so they were entrenched in Origin whereas this year I felt like I belonged," de Belin said.

"There was a lot of fresh faces as well who hadn't even been in an Origin camp before so I was a step ahead of all of those other players.

"Being in and around the camp last year, and being so close but not playing, it kind of made me hungrier and just being in the camp made me feel more comfortable so all of the nerves were gone."