The Jamaican sustained a double leg break in Leeds's game against Watford yesterday, which could keep him out for the rest of the season.
The Leeds boss told BBC Sport.: "He could be out for six months.
"I'm not devastated about the game but I am about Rudy. He has broken his leg in two places.
"I wanted to try and win the game with 10 men, but everything is irrelevant, it's the least of my worries when I think that we have lost Rudy for so long. When our lads knew about it, they were distraught."
Austin's injury left Leeds with only nine men on the pitch as Warnock had already made three substitutions, and Jason Pearce had been sent off.