Maroons coach Kevin Walters says he expects winger Dane Gagai to play in Wednesday's State of Origin opener despite a finger injury, while confirming Michael Morgan will start at fullback with Anthony Milford joining the bench.

The reshuffle follows Billy Slater's withdrawal due to a hamstring injury, with Newcastle fullback Kalyn Ponga on standby for Gagai.

The Knights young gun trained on the wing on Tuesday while Gagai was being treated for a possible compound fracture of the finger.

"Dane has come up with some sort of injury there," Walters told media on Tuesday.

"He's going off for scans and an x-ray this afternoon. He came back out and trained.

"We expect him to play given he came back out and finished off the session.

"Michael Morgan will be fullback for us and Anthony Milford will go onto the bench."

Queensland plans Ma-ruined - Gagai in doubt

Walters said it wouldn't be "fair" to ask Ponga to play at fullback in what would be his first State of Origin appearance, days after playing for the Knights in the NRL, and confirmed Ben Hunt would play after overcoming a cork and training strongly in the captain's run.

Morgan played a full season in the custodian role in 2014 for the Cowboys and was switched to fullback by North Queensland in the rounds preceding the Origin team going into camp.

The Maroons have decided moving Morgan to fullback brings the least disruption to their preparation and is the right fit for game night. The 26-year-old knows the Queensland systems and calls that are so vital in the spine.

Walters said Morgan had the talent and the temperament to handle a late positional switch.

"Morgs has been our Mr Fix-It now for several years and I think in his last couple of weeks at fullback for the Cowboys he has really turned around their attack," Walters said.

"Michael is a mature player and can handle the expectation that comes with playing for the Maroons."

Milford and Walters share a close relationship and the Broncos five-eighth will be given a licence to thrill.

"He can do some things on a footy field that not many players can and I think at this level that is very important," Walters said.

"I have seen some great touches from Milf, particularly in the last couple of weeks.

"He'll admit that his first Origin [in game one last year] was a disappointing one for him. The second time around we hope he gets the opportunity to really show his class.

"Our whole philosophy around Milf is for him to get the ball and let him run. That is his go-to play and when he gets on we want him to challenge the middle or anywhere on the field with his explosive running."