Wests Tigers coach Tim Sheens is confident 18-year-old halfback Jacob Miller can fill the void left by the injured Robert Lui as his side's injury crisis deepened.

The Tigers were rocked on Thursday after it emerged Lui would be sidelined for six weeks with the ankle problem he sustained in last Saturday's win over Canberra.

The victory proved costly for Sheens' team, with Chris Lawrence set to miss up to four months after dislocating his hip and Lote Tuqiri breaking his arm in the same match.

The trio join such stars as Gareth Ellis, Liam Fulton, Bryce Gibbs and Beau Ryan on the unavailable list, with Lui's absence forcing Sheens to name a sixth new face in the No.7 shirt in just over two years.

In that time Benji Marshall, Blake Lazarus, Robbie Farah, Tim Moltzen, John Morris have all had to fill in at halfback due to injuries.

Miller is preferred at halfback for Sunday's clash with the Sydney Roosters to Moltzen, who is named in the centres, despite the 22-year having yet to taste defeat in the eight games he has played alongside five-eighth Marshall since round 17 in 2009.

However, Sheens, said Moltzen, who will be starting his first game in almost a year following knee surgery, needs more game time before being used as a playmaker.

"Tim hasn't played much football in the last 12 months, he's really a running player for us at the moment, he's gradually coming back, but at the moment I am happy using him as a utility," Sheens said.

"We will have to wait and see what happens over next month, we'll see if young Jacob can handle it, but Timmy is there as an option."

Miller captained NSW U-18s against Queensland last year, and ironically will make his first-grade debut against his former club at the Sydney Football Stadium.

"He has been going very well, he played in two first grade trials, and from my point of view I am happy with where he is," Sheens said.

"Mitchell Pearce played first grade at the same age and if you are good enough you are old enough and I think he's good enough.

"Most of my guys have played first grade young, (Andrew) Fifita, Liam Fulton, Robbie Farah was a 17-year-old, and there is also Benji Marshall.

"Young kids seem more prepared for first grade now."

Skipper Farah echoed Sheens' confidence in Miller.

"He's a really good kid, he had a really good pre-season and is a smart halfback, he has a little bit of cheek in him which is needed for a kid, he won't have any problem bossing the boys about the park," Farah said.

Farah said he had taken heart from the way the team's young forwards, Simon Dwyer, Aaron Woods and Alan Schirnack had filled in for Ellis, Gibbs and Fulton.

"In the first couple of weeks the young kids stepped up well and now the outside backs get a chance," he said.

"Guys like Mitch Brown and Geoff Daniela have been waiting in the wings for their chance and they have that this week."

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