GWS forward Devon Smith has joined veteran midfielder Ryan Griffen as long-term AFL casualties.
While the Giants are flying after three-straight wins, including last week's demolition of Hawthorn, it is coming at a cost.
They confirmed on Tuesday that Smith would need knee surgery next week, sidelining him for at least two months.
After missing their round-four win over Port Adelaide, he returned for the successful away match against St Kilda and was again out of the side for the Hawthorn match.
Giants official David Joyce said they sought advice from a specialist last week and had several options to consider before deciding on the operation.
"The decision has been made to tidy up some of the cartilage in his knee that has been causing discomfort," he said.
"We believe surgery is the best option at this stage of the season so that Devon can successfully return to the field later in the year."
GWS had already flagged Griffen's absence for five to six weeks thanks to a fracture in his back.
Griffen left training in obvious discomfort last week but, at the time, the Giants thought he was alright.
He was then a late withdrawal from the Hawthorn win.