He had no idea why but the furthest thing from his mind was what he was about to be told.

"I had no clue what Browny wanted but making my NRL debut didn't even enter my head," Best admitted.

It was prop David Klemmer who cottoned on first to what was about to go down for the 18-year-old Woy Woy junior, whose father Roger played for Manly and the London Broncos.

"Tau [Moga] went into Browny's office first and I was standing there next in line and Klem leans over and says 'this could be your chance brother'," Best said.

"That's when the heart started pumping a bit faster. Tau walked out and I walked in and Browny just said to take a seat so I sat down and he said straight out 'what are your thoughts on playing this weekend?'.

"I asked him what he meant and he said 'you've got a debut this week on the left wing' and I just sat there pretty speechless. It was pretty crazy and I think eventually, I just said 'yeah, that would be great'.

Given the season he has had, Best's reaction was understandable.

He only became eligible to play in the NRL when he turned 18 just 13 days ago and because of a frustrating run of injuries, he has played only seven games all season.

He missed the opening few rounds after suffering a grade three medial tear in his knee on the Australian Schoolboys tour to England late last year and when he did return, he was plagued by hamstring and hip problems before an ankle injury sidelined him for six weeks.

He only returned last weekend, coming off the bench in the Knights' Jersey Flegg Under 20's win over North Sydney where he scored a hattrick of tries. Hardly a great preparation for and NRL debut in a crunch, must-win game against the Wests Tigers on Saturday at Campbelltown Stadium.

"Yeah, I was pretty shocked when I found out but it's a real buzz now," Best said.

"This has made a pretty ordinary year up to now a real special one. I've had a frustrating run with injuries. I was just happy to finally get back on the field last weekend and the goal was hopefully to play in the semis and try and help the boys win the Flegg comp. So for this to happen - like I said, I'm buzzing."

The first phonecall he made was to his mum and dad.

"I told the old man and he was over the moon and mum just broke into tears," Best said. "I'm not going to ever forget it."

Coach Brown admitted there was never any question Best would make his debut.

"It was always going to be when, not if but we had to wait until he turned 18 and was eligible first and he's had a tough run with injuries," he said. "He'll handle it no problems."

Best was first scouted by the Knights when he was just 13 and it was current Flegg coach and junior development boss Scott Dureau who made the decision two years later to turn him from a backrower into an outside back.

He starred at junior level, repping NSW at Under 16's, Under 18's and Under 20's and outside of Klemmer, no player in the club is signed for longer with Best a Knight until at least the end of 2022.

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Skipper Mitchell Pearce and fullback Kalyn Ponga are both looking forward to seeing how Best goes and confident he won't be overawed.

"He's got size, he's quick and he's a great young bloke who'll go good," Pearce said.

Ponga said: "He's a big boy. He looks like he's 30 but he's 18 and he's obviously excited and I'm excited for him."