Dylan Napa might never have played rugby league had it not been for one fairly important rule.  

"I played rugby union in high school, but when I left high school you couldn't shoulder charge in union so I switched to league," the Roosters firebrand said ahead of his 100th NRL game against the Sharks on Saturday night. 

"When I switched to league, they banned it! That's the main reason I switched codes and I'm pretty glad I did because I've met a lot of great people and I've made a lot of great friends in rugby league."

Even experienced code-hopper Sonny Bill Williams is having trouble remembering the rule after he was red carded and then slapped with a four-week ban for an illegal shot against the British and Irish Lions earlier in the year. 

Napa and his former Roosters teammate caught up ahead of the opening Bledisloe Test on Saturday in Sydney but didn't discuss whether the New Zealander would return to Bondi after he helped them to premiership success in 2013. 

"Probably as much as every rugby league fan I would like to see him back," Napa said. 

"He didn't say anything so hopefully he comes back but he's got a pretty good gig at the All Blacks playing inside centre so I'm not too sure."

There's nothing shabby about the career Napa has forged at the Roosters and there'll be added emotion when he runs out onto Southern Cross Group Stadium for his milestone match this weekend.

"I always think about my mum and dad and my brother and sister every game," he said. 

"I always have a think about them and I know how much it would mean to my old man (Stan) because he loves football so much and respects all the players so much. 

"The olden day era and the new modern day players, he's got so much respect for all the different generations of footballers so for me to play first grade and to be able to play it 100 times, I know how much it'd mean to him.

"I'm really proud of myself because when I first moved to Sydney when I was 17, I never thought that I'd even play one NRL game. To be able to say that I've played 100 games feels like I've represented my family and myself really proudly."