Luke Keary sidelined with a broken jaw

Luke Keary appears set to miss the start of the season after breaking his jaw at training.

An accidental head knock during a trill at training on Wednesday saw Keary go down grabbing at his jaw.

While the break isn't as bad as it could be, the enigmatic five-eighth will spend at least four weeks on the sidelines, putting him in major doubt of lining up against the Wests Tigers on March 10.

Roosters fans eager to see new recruits Cooper Cronk and James Tedesco link with the half will have to wait longer than expected to see the new look spine in action.

Having released Mitchell Pearce, Connor Watson and Jayden Nikorima during the last few months, Mitchell Cornish appears the man most likely to inherit the number six jersey.

Lachlan Lam, son of former star Adrian, is also a chance of snaring the spot, having made his international debut for Papua New Guinea at the World Cup, despite him never having played a first-grade match.

Trent Robinson will use the upcoming trials to determine who becomes the club's backup half, with their February 24 clash against Manly on the Central Coast the best indication of who'll start the season at six.