As revealed on Thursday, complications with an ankle injury the older sibling suffered against Canberra in round eight will prevent him from adding to his 179 first-grade appearances for the Sea Eagles. The former NSW and Australian back-rower had surgery in what will be his last season at Brookvale before switching to South Sydney.

Stewart's teammates were still coming to terms with the news at training at their Narrabeen headquarters on Thursday, a day after fellow forward Jason King announced he would retire at the end of the season. No one took the news harder than his brother, who will play against, rather than with, his sibling when they next take the field.

"He saw the surgeon yesterday and has gone under the knife today," Brett Stewart said. "At this stage, it probably looks like he will be done for the year. I feel a little bit sorry for him. As a brother, knowing we might not get that chance again to play together, it's been a tough week. I spoke to him last night. [He's] probably a little bit shattered, like all of us. But he's a tough man."

The loss of Stewart and King could be the first steps in dismantling one of the best teams of the current era.

The Sea Eagles are about to contest their 10th consecutive finals series, but the future of several key players remains clouded. Brett Stewart declined to answer questions about his long-term intentions. Another stalwart, Steve Matai, said his future was "up in the air". Anthony Watmough was another senior figure disappointed Glenn Stewart wasn't tabled a contract extension. Matai said the injury news came as a shock.

"Glenn's a really good mate of mine and to hear that is quite sad that he couldn't put the jumper on one more time for us," Matai said. "He's a big part of the culture here, we've been playing together for the last 10-11 years. There's been a good group of core players that have been here during that time. We've definitely built a good culture and he brings a lot to that. On the field he's just a great ball player, great runner of the ball and great defender. He'll be sadly missed."

Manly coach Geoff Toovey spoke about the void Stewart will leave. "Very disappointing for the club and for Glenn, a Clive Churchill Medal winner, grand finalist, Australian player," Toovey said. "It would have been great to run onto Brookvale Oval again this weekend and play in the home [environment]. Touch wood it's not over yet, but it doesn't look good."

Manly forward James Hasson said: "That will be a massive blow, I've enjoyed playing with 'Gift'. His performances week in and week out, you know he's a competitor. He's always putting his best foot forward. If any of the boys put their foot out of line, he's always the first one to pull them in and get them back on track."

Sitting on top of the ladder and all but assured of a top-four finish, Manly still have much to play for when they host Penrith at Brookvale Oval.

It will be King's last home game and Matai's 200th NRL appearance. Brett Stewart is just three tries short of Steve Menzies' record of 75 at Brookvale Oval. One of the highlights will be the clash between Stewart and Panthers custodian Matt Moylan.

"He's definitely another player to watch, him and [Jamie] Soward have got a great combination going," Stewart said.

"He's another player who can damage us ... He will be a player we'll be watching on Sunday, for sure. I enjoy watching him play, it appears not much affects him. He's a pleasure to watch."