Glenn Stewart has knee surgery and faces 10 weeks on sideline; Panther out for six There's fears Manly forward Glenn Stewart will miss the first three months of the NRL season with a knee injury. Knee surgery: Manly's Glenn Stewart faces a stint on sidelines. GLENN Stewart will miss the first month of the NRL season and could be on the sidelines for up to 10 weeks after having off-season surgery for the second time. Stewart had surgery to clean out floating cartilage in his left knee on Thursday and will see a specialist again this week in a post-operation check-up. There is no structural damage or issue with ligaments. It comes as Penrith general manager Phil Gould this morning revealed promising speedster James Roberts, who was a standout in Penrith's trial win over the Tigers on Friday night, had injured his ankle and would be out for six weeks. Stewart's rehabilitation program has been designed for a 10-week turnaround which would allow him to return for the Sea Eagles' round seven clash with the Rabbitohs at Brookvale Oval on April 26. Stewart had the same minor cleanout surgery at the end of the 2012 season. It is a major headache for Sea Eagles coach Geoff Toovey with the Sea Eagles suddenly short on backrowers following the departure of Tony Williams to the Bulldogs. Meanwhile Roberts has been placed in a medical "moon boot" and will today see a surgical specialist to have X-rays and decide if his injured ankle requires surgery. If no surgery is required he will make his debut for the Panthers in round three against the Rabbitohs at Centrebet Stadium.