The 31-year-old forward will go under the knife to repair his troublesome elbow injury, which he aggravated in a charity boxing bout against All Black Hika Elliott in in New Zealand over the weekend.
“I scheduled this surgery three weeks ago, so it had nothing to do with the fight. I’ve just got a little bit of floating bone and I’ll get that cleaned up,” Gallen told Cronulla’s official website.
“I’m expecting to be back on deck and in full training when we come back after Christmas on January 7.”
Sharks coach Shane Flanagan meanwhile dismissed reports that the injury was suffered in the fight, which Gallen won on points.
“The boxing match had nothing to do with it” Flanagan said.
“It was an injury sustained at training and the extent of the injury has been blown out of proportion. He will have the minor surgery on Thursday and we don’t expect him to miss a day of training once we resume after Christmas.”
Gallen is expected to play a part in the annual NRL All Stars match and the Sharks’ trial game with Gold Coast.