Anthony Seibold has refused to commit to Tom Trbojevic being Manly's fullback for the rest of the season.

The Sea Eagles' talisman has plied his trade in the centres for the past five matches, but has regained the No.1 jersey this week amid Lehi Hopoate's injury.

Trbojevic had admitted recently that he expected to finish the year in the centres, until Hopoate's injury prompted his shift to fullback in Round 23.

"It's always been a week-to-week decision," Seibold said ahead of his side's crucial meeting with Canberra.

"Every decision I make is what I think is best for the team for that particular week. I think Turbo going back to fullback this week is the best thing for our team."

Hopoate has played fullback throughout the campaign due to Trbojevic's various injury setbacks.

The 20-year-old played there for the first time this season in Round 3 as the Sea Eagles romped to a 40-12 win over the Raiders.

He has since registered 11 games in total at the back, including the past seven matches in a row when he's been available.

However, the coach revealed the young gun had been playing hurt during the past few weeks and needed some time away to rest and recuperate.

"Lehi needed some time out and we've got a pretty good fullback coming in," Seibold said.

"He hasn't been able to do contact at training for some time with his AC joint, and then he copped another bang on his head when James Tedesco went through and there was an accidental collision [last week].

"He had another HIA, and he's had a few of them recently, and he's pretty banged up with the AC. So, the best thing for us on another short turnaround was to try to let that settle.

"We've spoken about this being Turbo's best position," Seibold added. "But we've also made a decision on what's best for the team over the last couple of weeks."