Michael Hooper is expected to be out for at least a month with a hamstring injury but Simon Cron said it will be "a bit of a nanny state" if the Waratahs are without Israel Folau in a crunch Super Rugby clash with the Rebels on Friday. 

Captain Hooper limped out of Australia's defeat to Ireland in the final Test in Sydney on Saturday and is not expected to play any further part in the regular Super Rugby season.

"I know our physios are working with the Wallabies physios around the time frames and from what I understand it's minimum this stage four weeks," said Waratahs forwards coach Cron.

"We'd hope to have him back in our finals series ideally. It's very early, so they'll keep working through it."

Wallabies full-back Folau faces a World Rugby disciplinary hearing after he was cited for an early aerial challenge with Peter O'Mahony.

Folau was also sin-binned for another incident involving the Ireland captain and Cron does not believe he should face further punishment ahead of the Australian Conference leaders' showdown with the second-placed Rebels.

"I'd be stunned if he's not available," he said. "Personally, I think it's an interesting decision to even send him there [to a disciplinary].

"They've made that call, so he'll go and defend himself. You probably saw it, personally I think if you're in the air and you're three foot off the ground, four feet off the ground, he's quite high off the ground.

"I would think they would look at their one-man lifting technique. I know we do a lot of it but I'd be surprised. It'd be a bit of a nanny state if they pull him."