Trbojevic has just returned from a stint in the US with reconditioning specialist Bill Knowles after aggravating a recurring hamstring issue.

The Manly No.1 has struggled to last the duration of the season in recent years and that led to calls from outspoken Sea Eagles stalwart Peter Peters suggesting the club should plan for life without the 26-year-old.

Peters likened Trbojevic to a flash sports car which couldn't be driven due to a mechanical fault.

But Seibold dismissed those concerns, highlighting that a fit Trbojevic would be critical to their fortunes in the NRL this season.

"It came from a former player of our club and it was disappointing to hear that in the public domain," Seibold said.

"He is an important player to our club and where we want to get to.

"It's easy to make a comment like that, and I don't think it was an educated comment."

Trbojevic - a former Dally M Medal winner - has been critical to Manly's success or failure in recent years.

Since 2019, the Sea Eagles have enjoyed a 68 per cent winning rate when he is on the field.

The fullback said the work with Knowles often went "above my head" but he claimed he felt more comfortable that his body wouldn't break down.

"I think it gives me a lot of confidence and it definitely helps you mentally as well," Trbojevic said of his time with Knowles.

"He's not necessarily worried about the hamstring, he's worried about making you a better athlete.

"Injuries come because there's a chink in the armour, (it's a focus) on athletic performance and getting everything working as a symphony."

Australian Associated Press