David Lyons, who was named at lock for Saturday's clash, is also in doubt.

Palu is the fifth Waratah forward to succumb to injury, joining Phil Waugh, Daniel Vickerman, Alex Kanaar and Dean Mumm on the sidelines.

He will undergo an MRI scan this afternoon.

"The quality of players at our match day promotional events will be at an all time high," a philosophical Waratahs head coach Ewen McKenzie said.

"At this stage I'm thinking of giving (assistant coach) Steve Tuynman a run off the bench - at least he knows the lineout calls.

"In all seriousness though, we've been relying on a relatively small group of players in key positions for some time and wear and tear is inevitable.

"If anything at least this gives Wycliff the chance to freshen up, and while we're still sweating on David Lyons we'll take a look at our options when it comes to the make up of the back row."

Lyons is rated a better than 50-50 chance of playing the match after suffering a corked thigh at training on Tuesday.

The final make-up of the team to play the Crusaders will be confirmed on Friday.