But it was clear what had inspired the winger's stunning two-try display in Brisbane's 24-12 NRL win over Penrith at Suncorp Stadium on Friday night.

Just three letters were scrawled on Isaako's wrist when he ran out against the Panthers - Dad.

It was a poignant nod to his father, who is battling incurable cancer back in his hometown Christchurch.

And clearly it also provided no shortage of motivation for the 23-year-old.

Isaako bounced back to his best in the Broncos' round-22 victory that kept their top eight hopes alive, scoring twice in 10 minutes as the goal-kicking flyer racked up a personal tally of 16 points.

"I feel as though that was his best performance of the year," Broncos coach Anthony Seibold said.

"Obviously he's got some challenges that we are all aware of from a family point of view.

"But he is in really good shape physically and he is in a really good head space."

Isaako was told a day after making his Test debut for Samoa in June that his dad Taai had been given just weeks to live.

He raced back to New Zealand to be with his father, missing two NRL games.

However, after responding to treatment, his dad insisted Isaako return to Australia.

His father is now able to watch his son's NRL games on TV - and he would have no doubt loved what he saw on Friday night.

Isaako reproduced the form that earned him 2018 NRL Rookie of the Year honours, running 188m and notching two line breaks plus five tackle busts in a devastating display.

Grinning ear to ear, Isaako punched the air in jubilation each time he crossed after first running off centre Kotoni Staggs in the 44th minute then pouncing on an Anthony Milford grubber 10 minutes later.

Clearly footy is fun again for Isaako.

Seibold also couldn't be happier.

"It's really pleasing to see the pace and running with intent that he did," he said.

Isaako helped spark a Broncos attack that Seibold admitted was "scrappy" in last round's underwhelming win over North Queensland, just in time for their finals tilt.

Brisbane provisionally leapfrogged Penrith into seventh spot with three rounds left.

"I just thought we ran with plenty of intent. There was a lot of purpose with what we did, we were more calm with good ball," Seibold said.

"It was a good step in the right direction from an attacking point of view."

Australian Associated Press