GREATER Western Sydney has suffered a further blow to its midfield stocks with Devon Smith set to miss at least two months of footy with a knee problem.

Smith has struggled with his left knee for the last two months and will have surgery next week after initial treatment for a cartilage issue failed to fix the problem.

He is expected to be sidelined for 8-10 weeks.

The 22-year-old had an interrupted pre-season and was forced him to miss the NAB Challenge, but returned for the first three games of the year, in which he averaged 17 possessions and a goal.

Smith then missed the Giants' round four clash with Port Adelaide, returned to play St Kilda, but couldn't get up for last week's stunning 75-point win over Hawthorn.

Giants' head of athletic performance David Joyce said surgery was in Smith's best interests and gave him a chance to return for a potential finals campaign later in the year.

“We consulted with a specialist late last week and after weighing up a number of options in recent days, the decision has been made to tidy up some of the cartilage in his knee that has been causing discomfort," he said.

In slightly better news for GWS, Ryan Griffen has avoided surgery but is still expected to miss 5-6 weeks after suffering a small fracture in his lower back at training last week.

The experienced midfielder was a late withdrawal from round six after copping an accidental knock on Wednesday, with Giants' officials shocked to learn how serious the injury was.

Forward Will Hoskin-Elliott (quad) is set for a month on the sidelines, while Sam Reid (hamstring) and academy draftee Matthew Flynn (ankle) will both miss at least a week after being injured in the NEAFL on Saturday.