Brett Stewart continues to be hampered by hamstring trouble with the superstar fullback in significant doubt for Manly’s NRL season opener against Canterbury.

Stewart didn’t train with the Sea Eagles at their Narrabeen base on Monday morning, instead opting for treatment with the team physiotherapist.

The superstar fullback was injured in Manly’s trial win over Ipswich two weeks ago.

Stewart has been hampered by hamstring trouble for much of his career and the injury hasn’t progresses as well as hoped. He is rated a 50/50 proposition for the Manly’s round one clash against Canterbury at Brookvale Oval on Friday night.

New Manly playmaker Dylan Walker said he was unsure as to the availability of Stewart.

“I’m not too sure,” Walker told reporters on Monday.

“It is our first day back after the weekend, it is up to Trent to decide.”

Recruit Apisai Koroisau is likely to play. He trained on Monday and shared the hooker duties with Matt Parcell as new coach Trent Barrett put his side through their paces.

“Api will play, he is going awesome,” Walker said of his flatmate and former South Sydney teammate Koroisau.

Gun rookie Tom Trbojevic will play against the Bulldogs. He picked up a leg injury against the Jets but has recovered quickly and trained strongly on Monday.

“Tom Trbojevic has been fantastic over the off season,” Walker said.

“His speed is second to none and I never knew how strong he was until I got here.

“He has been phenomenal since I have been here, there are a lot of good things ahead of him.”

Trbojevic will likely slot into fullback if Stewart is ruled out.