There is only one Nathan Cleary.

That's a truth new Dolphins playmaker Sean O'Sullivan learned in a defining season at Penrith in 2022 as Cleary's understudy.

Finding his own identity has been the key for the 24-year-old as he prepares to own the No.7 jersey at the NRL's newest franchise under coach Wayne Bennett.

"I have realised who Sean O'Sullivan is," he told AAP.

"The foremost thing I learned from Nathan is being comfortable with who you are and being able to play your own football.

"I know Wayne doesn't want me to be anyone but me. I am trying to prove to him that I am the man for this job."

The Panthers won each of the first five games O'Sullivan played in 2022 when Cleary was absent with injury or on State of Origin duty. He had a blinder in the opening-round 28-6 win over Manly, and guided Penrith to wins over Canberra and South Sydney at the back end of the year when Cleary was suspended.

Dual-premiership winner Cleary puts his own stamp on what a great No.7 can be. He doesn't try to be Allan Langer, Andrew Johns, Cooper Cronk or Johnathan Thurston, but he embraces the clutch moments just like they did.

"When you are comfortable in your own skin like Nathan is you are walking towards those big moments," O'Sullivan said.

"I am forever in his debt for the confidence he gave me and what he taught me about footy and how to build a game in eighty minutes. I will be taking those lessons into the coming season that is for sure.

"Penrith didn't want me to be Nathan. They just wanted me to be Sean.

"As a result I realise what my strengths are and just have to nail my own role. I know the other sixteen players in the team will be doing theirs too. That is what we are looking to build here at the Dolphins."

O'Sullivan had a series of serious injuries early in his career, but when Bennett was Broncos coach he signed him from the Sydney Roosters for the 2019 season. Several weeks into pre-season, Bennett was sacked.

"I was looking forward to being coached by Wayne back then but didn't get the opportunity," O'Sullivan said.

"Now I am very excited. Finally, the timing is right.

"My journey has been one of setbacks and a lot of highs but now I am a lot more confident in myself as a person and a player.

"It is pretty cool that I am in this position to hopefully not only lead the boys here at the Dolphins, but also get around them and learn as much as I can.

"Last season was a massive one for me, being under Nathan. I learned so much at Penrith."