Maroons selectors have kept their nerve with the inclusion of 20-year-old prodigy Kalyn Ponga on the bench Origin II to be played in Sydney this Sunday the only change to the Queensland side originally selected for Origin I.

Queensland prop Dylan Napa will be given until Wednesday to prove his fitness with Melbourne's Tim Glasby on standby to come straight into the 17.

If Napa plays, Bill Slater's return at fullback for Michael Morgan, who has suffered a season-ending bicep injury, and Ponga replacing Anthony Milford on the interchange bench will be the only changes to the side beaten 22-12 at the Melbourne Cricket Ground in game one.

Coach Kevin Walters said he had no concerns over Slater recovering fully from his hamstring injury and playing his 30th game for Queensland, claiming the Test fullback could have played for the Storm on Sunday.

Ponga, the most brilliant player on rugby league's horizon who will play State of Origin after just 24 NRL appearances, will be the least experienced Maroons player since Brent Tate made his debut in 2002 after just a handful of games for Brisbane Broncos.

"He's a been a standout in the competition," Walters said of Ponga.

"I think everyone's seen how good he's been for the Newcastle Knights. He's got the potential to be a long-term player for Queensland and I think he has earnt the right to put on a Maroons jumper.

Walters gives Napa Wednesday deadline

"It's time for him to show what he can do, without putting too much pressure on him.

"For Kalyn it's a great opportunity for him. We're very grateful for having him in the side this time around and we expect him to do his job for Queensland on Sunday."

Walters and selectors Gene Miles and Darren Lockyer have stuck by the pack that was dominated by the Blues big men for much of the match in Melbourne, particularly prop Jarrod Wallace who was under pressure after a below-par performance in attack in game one.

They will miss Napa's aggression if he succumbs to an ankle injury suffered on the weekend, even though he was disappointing in the opening Origin clash.

If he misses, Walters is likely to move Josh Papalii into the starting front row, with Josh McGuire moving up from lock and Jai Arrow starting at No.13 the other most likely option. Either way, Glasby would come off the bench.

Maroons squad (in likely starting order): Billy Slater, Valentine Holmes, Greg Inglis (capt), Will Chambers, Dane Gagai, Cameron Munster, Ben Hunt, Jarrod Wallace, Andrew McCullough, Dylan Napa, Gavin Cooper, Felise Kaufusi, Josh McGuire. Interchange: Kalyn Ponga, Josh Papalii, Coen Hess, Jai Arrow. Tim Glasby (18th man).

Don't miss Game II of Origin at ANZ Stadium on Sunday 24 June. Get your tickets here