It was when current Dolphins mentor Wayne Bennett was leading the Rabbitohs that the now 33-year-old Nicholls came of age as a footballer.
When Bennett arrived at Redfern in 2019 he played Nicholls in round one.
Previously a sporadic NRL player, in Nicholls' three years under Bennett at Souths he was picked every week unless injured.
"At that stage of my career I was 28 and it was a 'now or never' season," the Dolphins prop said ahead of Thursday's clash with Souths at Suncorp Stadium.
"I had mainly been a reserve grader and Wayne turned up and said, 'I am going to play you in first grade', about eight weeks before round one.
"He said, 'You are a first-grade footballer in my eyes'. For someone of Wayne's standing in the game to stand there and say that about me when he had only been there for a month put a bit of confidence in me.
"From that day on, I didn't want to let him down. I still don't want to let him down."
Nicholls played 100 games for the Rabbitohs before joining the Dolphins in 2022.
"That club is always going to have a special place in my heart but I want to win Thursday night for the Dolphins," he said.
"I know as well as anyone they have strike all over the park.
"We are going to have to turn up and be willing to play with the effort we played with (in the 32-22 win over North Queensland in round six)."
Nicholls said he was thankful to Rabbitohs coach Jason Demetriou and CEO Blake Solly for allowing him to explore the option of joining the Dolphins in a bid to extend his career.
"Wayne said, 'Do you want to come and have some fun?' in a text message and … I said yes," said the player, who had enjoyed living in Queensland during the COVID-19 bubble.
"Me and my wife knew it was the right decision for us as a family and we've loved every minute."
The Dolphins, who get captain Jesse Bromwich back against the Rabbitohs after a throat infection, have won four from six to sit inside the top four.
