Tom Jenkins has revealed how being regularly overlooked at Newcastle gave him the "kick up the bum" he needed to be a starter for four-time premiers Penrith.

Jenkins completed one of rugby league's most unlikely comebacks last week, starting at fullback in a senior game for the first time in Penrith's loss to Melbourne.

The 24-year-old is set to keep his spot in Penrith's side for Thursday night's clash with South Sydney, lining up on the wing if Daine Laurie is fit to wear the No.1.

A Young Cherrypickers product who played six games for Penrith in 2022 and 2023, Jenkins loomed as a backline threat when he moved to Newcastle for an opportunity last season.

But he played only five games, was released from his contract early and returned to Sydney without a deal and only plans of training with St Mary's Ron Massey Cup side.

"I was probably promised a lot of things at Newcastle and it was on both ends," Jenkins said.

"I probably didn't live up to expectations. It was purely me getting ahead of myself. You could say I regret it, but everything has a reason, everything has a why.

"I took the gamble of not knowing what was next (moving back).

"It's probably exactly what I needed, a bit of a kick up the bum."

Jenkins' St Mary's stint lasted just one day, told to divert his car to Penrith by NSW Cup coach Ben Harden while on his way to St Mary's training last November.

Even still, the outside back spent the summer working as a support worker for a friend's disability company, before signing a full-time NRL deal in February.

"I just did that while training in the arvos," Jenkins said.

"That's something I'm really passionate about, I love that, I still work there on my days off when I can.

"When I made the decision to leave (Newcastle), I didn't know what was next, I knew that Penrith's a hard system to crack.

"It wasn't something that I knew I was going to come back to ... there was no promise that you'll be full-time soon."

Stuck behind now-former Panthers Sunia Turuva and Taylan May when initially at Penrith, Jenkins said both he and coach Ivan Cleary agreed he should move on.

But the Riverina junior admitted he struggled in Newcastle and always felt like he should be back in Sydney, before taking the punt on moving home and eying off a Penrith return.

"I probably needed to leave, to go away, chase an opportunity for my own development and career," Jenkins said.

"I don't regret it, it's exactly what I needed to go away and experience different things, experience a different club.

"The opportunity to come back was a long road, and it definitely could have been a lot different.

"But it was a risk I was willing to take to get back here. If I didn't go away I might not be here now."