Mann battled an ankle injury in the closing minutes of the win over Canberra on Sunday and there were fears after the game that he may be facing a stint on the sideline.

With Connor Watson having already undergone ankle surgery after suffering a syndesmosis injury against Penrith that could keep him out for a further five weeks, losing Mann as well would heap further pressure on the Knights depth.

As it stands, O'Brien has brought 20-year-old playmaker Phoenix Crossland onto the extended bench for the Storm game as insurance if Mann is ruled out.

It's likely he would come onto the bench with Tex Hoy moving to five-eighth to partner skipper Mitchell Pearce in the halves if there is a forced change.

But Mann showed last year when he played half the season with pain-killing injections for a sternum injury that he can handle some discomfort when called apon if there is no risk of suffering any further damage.

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"Kurt is looking pretty good actually," O'Brien told the Newcastle Herald on Tuesday. "There is still some swelling there and he's having some scans done but they are just precautionary actually.

"We are just making sure it's not more than we think it is because he has had surgery on that same ankle before. We are making sure there is nothing nasty there and if that's the case, the rest of the week will be about reducing the swelling and pain management.

"I'd say at this stage he is a definite chance which is why we have named him in the six jersey."

O'Brien confirmed Crossland, who made his debut off the bench last season against the Bulldogs, will likely come into the 17-man squad if Mann misses out.

"Phoenix has been going really well at training. His contact [in defence] has been good and I know he's got a good kicking game," he said.

"Whether he or Tex would slot in at six if Kurt doesn't come up I haven't completely made up my mind. I wouldn't say Phoenix is not without a chance though."

The inclusion of Crossland means back-up hooker Chris Randall drops out of the squad altogether.

"You can't go too small on your bench," O'Brien said. "I need to name middles and I need to name backrowers because if you get off the bus with temperate checks, having Phoenix, Tex and Randy there isn't going to help me if Klem [David Klemmer] gets off the bus and he's got a temperature.

"I'm also mindful of guys being in our 21 for the past two weeks and having to keep them fresh in case we need them on game day - we can't keep naming them.

"That's why I've put Tau [Moga] and Kingy [Josh King] in and taken Pasami [Saulo] and Gehamat [Shibasaki] out because Tau and Kingy have been loaded up with training while Pasimi and Gehamat have been protected from that a little bit. So this week, the roles will be reversed."

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