Thump ... thump. "What's that," asks the visitor to the Broncos' headquarters about the repetitive thud on the window.

The staffer looks over the training ground next door, at the empty field except for one lone person and 20 footballs scattered on the ground.

"That's just Jamayne practising his kicking," he explains. "He's getting plenty behind them today."

It's more than that though. It's history in the making.

Broncos winger Jamayne Isaako is by himself on his day off, doing the 90-minute weekly session he never misses. It has helped him become the highest scoring rookie player in Australian rugby league's 111-year history.

The 23-year-old winger, who wasn't even first choice goalkicker when the season began, is also the first top point-scorer in his rookie year since fellow Kiwi Daryl Halligan rattled up 196 points in 1991 for North Sydney (including finals matches).

Isaako's tally of 233 points from the regular season, sure to grow from at least one finals match, has beaten Michael Cronin's 1977 effort of 225 points (including finals) in his first season at Parramatta that also landed him the Rothmans Medal and a grand final appearance.

However, Cronin was hardly a rookie in the real sense, having played for Australia from country Gerringong since 1973. In Cronin's defence, tries were only worth three points.

If Isaako, who played one match in 2017, also lands the rookie of the year title, he will also be the first player to pick up both gongs on Dally M awards night.

And the key to that success has been his schedule of preparation ... and a decent dose of ice-cool temperament and quiet confidence.

Isaako will never miss two 30-45-minute kicking sessions after training each week, nor his day-off routine that has been his making.

The Broncos have given him a key to the gear room. So every scheduled midweek day-off he'll have breakfast, head to Red Hill, grab two bags of balls, head onto the field and for an hour and a half, and go through his routine.

There's no ball retriever, just Isaako and his tools – a kicking tee and footballs.

And if the wind is behind him or he's whacking them like a three-wood down the middle from short range ... those in the adjoining office certainly know it. Fortunately, the building's glass is heavy duty.

"I like it that it is always nice and quiet and peaceful when I'm practising and, going into a game with a crowd being able to put you off, I think back to practice, put myself in that sort of mind frame and it has really paid off," Isaako said.

"Goalkicking is something I really pride myself on but I didn't come into the season thinking I was going to be the goal-kicker.

"I was fortunate that after Jordan [Kahu] went out [injured] in the Cowboys game it allowed me to take on the kicking duties and I have kept the job since. All the practice throughout the season has paid off.

"I grew up idolising [All Blacks icon] Dan Carter and I know he did a lot of practise kicking, so I've always tried to do that. And it helps me mentally prepare for each game."

Isaako, who made his Test debut for the Kiwis in June against England in Denver, admits he didn't expect to start the season in the Broncos' 17, let alone not miss a match.

What do you love about the finals?

He was hoping to make the side once State of Origin came around and key men would be missing or injuries set in.

Going into this Sunday's elimination semi-final against the Dragons, he is a key part of the Brisbane back-line after having scored 11 tries and 94 goals at a kicking success-rate of 84 per cent.

"Being able to keep my good form and play every game has been a real achievement that I'm really grateful for," he said.

"It's finals time now and I just have to keep doing what I have been doing, relax and stick at the extra training."

Thump ... thump ... Jamayne is back.