Manly Sea Eagles head coach Anthony Seibold has revealed towering winger Jason Saab could be set to spend as many as six weeks on the sidelines.

Saab pulled up with a hamstring injury late in the final minutes of Manly's Round 1 win over the South Sydney Rabbitohs during the historic season-opener in Las Vegas.

It came after he had run for almost 250 metres and scored a try in the game for Manly, with the towering winger in fine form to begin the season.

That will now be on delay though, with Seibold saying Saab likely has a Grade 2 hamstring tear that could leave him sidelined for six weeks.

It's also understood Karl Lawton may not be fit for Round 2 when the Sea Eagles play the Sydney Roosters with an ankle injury.

The news will come as a rude shock to Manly fans who had been left expecting Saab may return as early as Round 3 based on coach Anthony Seibold's comments in the post-game press conference.

"Anytime you see one of your real speed men pull up like that, it's not ideal. Obviously, he'll get scans when we get back to Australia," Seibold said post-game.

"We've got a long turnaround and it's probably doubtful he'll play in that Roosters game but whenever you see a player come off with a hamstring injury it's never going to be a five or seven day turnaround."

Manly have a number of options to play in place of Saab over the coming weeks. Raymond Tuaimalo Vaega is the most likely in a straight swap, while Tommy Talau, who signed from the Wests Tigers during the off-season, was close to making the team as it was prior to kick-off and could play at either centre or wing.

If he was named at centre, Reuben Garrick would move back to the wing.

Seibold acknowledged both options during his press conference post-game, but refused to nail down a replacement, and won't have to until next Tuesday.

"We've got Ray Vaega who was fighting really hard with Jaxon Paulo for that left-wing position...and another one I thought was a standout over the pre-season and unlucky not to be in the team was Tommy Talau," Seibold added.

"Tommy was really good for us. I think Tommy can play on the wing, play centre, so we've got a couple of options there."

In better news for Manly, Reuben Garrick will be fit to play in Round 2.