The worst part is the hole the surgeon cut in his guts to get the stem cells they injected into his troublesome knee.

He hopes the procedure will ease the pain of the chronic condition, which was threatening to end his storied 291-game career.

Croker had surgery on Wednesday and will spend the next month taking it easy before he can start to do some work on the bike and in the pool at the 4-6 week mark.

Then after 6-8 weeks he should be able to use the anti-gravity machine to begin running, with the plan to be back in full training by the New Year.

Once that hole in his guts has healed, he'll be able to start working on his upper body and core as well.

His knee limited him to just 12 games this season, with the 31-year-old undergoing multiple platelet-rich plasma injections throughout the year to help treat it.

Now he's turned to stem-cell treatment to try and get a more permanent effect.

While the surgery means he has to hold off chasing son Rory around the house, the fact he has him and his wife Brittney meant he wasn't worried about the future.

"You always think the worst when you're injured. But I'm not worried mate," Croker said, speaking for the first time since surgery.

"I've got a wife and a kid and beautiful family so I've always got that to come home to.

"You always think the worst, but hopefully this little procedure works and we can go forward."

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Croker said the surgeon was happy with how it went, now it's just a waiting game to see the effect it has.

If it works, he said he'd look at doing it again when he retires to help with life after football.

He said playing in the centres meant he had to be running at his best - defending on an edge in the NRL was hard enough already.

Croker's going into his 14^th NRL season, having become the Raiders' highest ever point scorer - with his 2238 points the third most of all time behind just Cameron Smith and Hazem El Masri - as well as their all-time leading try scorer with 133.

He needs 28 more games to surpass Jason Croker for the most games played for the Green Machine.

"The holes in your guts are a bit sore ... just getting up and down and moving, that's the worst bit," Croker said.

"It's mainly [for] pain relief. It can regenerate cartilage, but the main reason is just a pain-relief source for me.

"It's a bit of an unknown I guess. Once I do get back into training hopefully the pain relief's there."

Croker paid tribute to all the departing leaders from the club in Sia Soliola (retired), Dunamis Lui (uncontracted) and Ryan James (Brisbane) - but especially Soliola.

Soliola arrived at the Raiders ahead of the 2015 season - Croker's first as Canberra captain - and the latter was eternally thankful for his experience.

"Don't get me started on Sia, you could write three pages on Sia. Everyone knows how good a guy he is and what he means to the club and the community, and what he's done for Canberra in general," Croker said.

"Just myself, selfishly, what he's done for me - I couldn't have become a captain at 24 and lasted seven years, or whatever it's been, without having Sia there from day one.

"Sia knows that, he won't admit to that or agree to it, but we're certainly going to miss him."