EMERGING Port Adelaide onballer Robbie Gray is in doubt for Sunday's season opener against North Melbourne with a hamstring complaint.

Gray, 21, suggested his body was ready to withstand the rigours of regular AFL football by getting through the entire pre-season unscathed, but it could let him down at the first real hurdle.

He failed to train with his teammates at AAMI Stadium on Thursday morning, though captain Dom Cassisi said it was too early to say whether Gray would be fit to take on the Roos.

"Robbie's in a little bit of doubt and he's probably 50-50 to play," Cassisi said.

"The injury's not anything serious. He played in the last practice game against Collingwood and there's still three or four days to go until the game so he's still got every chance of playing."

Mercurial forward Daniel Motlop (hamstring) completed parts of Thursday's session, but is still no certainty to play against his former side.

The untimely injuries could open the door for impressive pre-season performers Mitch Banner and Daniel Stewart to make their AFL debuts.

Draftee Andrew Moore, ruckman Matthew Lobbe and recruits Scott Harding, Jay Schulz and rookie Cameron Cloke are also in the mix and Cassisi predicted there would be at least three new faces in the side.

"I think those guys have all done enough to get a game and whoever doesn't get picked will be very stiff, but they can hold their head up high knowing that they've done everything right and opportunities will arise during the year," Cassisi said.

"The injuries give an opportunity to some of the younger boys if they don't get up, like Mitch Banner, Matty Broadbent and those guys. We've definitely got some options there, but we'd like to have Motts (Motlop) and Robbie out there."

The Power have tapped into new assistant coach Dean Laidley's intimate knowledge of his former club as part of their preparations.

The Roos might have changed their game plan under rookie coach Brad Scott, who replaced Laidley in August, but Cassisi said his teammates had been given some extra insight.

"Dean's done a fair bit of work this week. We haven't gone through the whole list player by player, but he's definitely made it clear that if you want to ask any questions about certain players you can ask him," he said.

"You can do as much study on the opposition as you want, but unless you win the contested footy you're not going to give yourselves a chance to win."

Cassisi will play his 150th game this week, while midfielder Kane Cornes will play his 150th in a row.

Cornes has not missed a game since round 17, 2003.

The only other current player with a longer streak is Sydney Swans onballer Brett Kirk (176 games).