NSW is expected to be without Nathan Cleary for the entire State of Origin series after scans revealed the extent of his hamstring injury.

Penrith confirmed on Sunday morning Cleary had sustained a grade-two hamstring tear in the Panthers' 16-10 win over Canterbury on Friday night.

The Panthers said Cleary would be sidelined for eight weeks.

It is another injury blow for the Blues following the confirmation Tom Trbojevic will be unavailable for seven weeks due to a hamstring injury.

Trbojevic was injured in Manly's 30-24 loss to the Dolphins in Brisbane on Thursday night.

On Friday, Panthers coach Ivan Cleary said he was resigned to be without his son on the field for some time.

"It's very disappointing for him," Ivan Cleary said. 

"He felt it straight away, that would suggest it's … decent.

"It hasn't been an ongoing thing … He's basically trained for two weeks without any drama.

"I'm torn between his coach and his dad right now as well."

Cleary missed the last two matches of the 2023 State of Origin series because of a hamstring injury.

This season, he had only recently returned from a hamstring injury that sidelined the three-time premiership winner for a month.

A potential replacement for Cleary would be Cronulla halfback Nicho Hynes.

But Hynes is also under an injury cloud after sitting out the Sharks' 25-18 win over the Storm in Melbourne on Saturday night due to a calf complaint.

Prior to learning the extent of Cleary's injury, Hynes said he was hopeful he would only be sidelined for one match.

"It's going to be a day-to-day process and it would have been too much of a risk today but hopefully I can get up for next week," Hynes told Fox Sports on Saturday night.

"I've just been focusing the Sharks and getting us at the top of the ladder and I feel like I've done a really good job to get us into that position, helped by my teammates.

"I don't think I've ever been more ready to pull on a (Blues) jersey in the halves and play six with Nathan or seven if he's out.

"I feel like I've done what I could … and hopefully I can get back and play some good footy to get picked."

The State of Origin series begins in Sydney on June 5 and concludes in Brisbane on July 17.