Sydney coach John Longmire is convinced the Swans have the depth to cover both the shock retirement of defensive stalwart Craig Bolton and injuries to several other experienced backs heading into the new AFL season.

Bolton, 30, who was sidelined by an Achilles injury for most of last season, suffered ankle damage while running laps on Monday and will undergo an operation next week to reattach a tendon.

Sydney will also open their season against Melbourne at the MCG on Sunday without established backs Nick Malceski (knee), Tadhg Kennelly (knee) and Lewis Roberts-Thomson (hamstring), plus recruit Matt Spangher (quad).

Longmire said the injuries meant the club had opportunities during the pre-season to give younger players more exposure, while others had thrived last year after Bolton got hurt.

"We've seen Heath Grundy really develop as a key defender and we've seen Ted Richards do the same thing in the back half of last year and Lewis Roberts-Thomson in the first half of last year really develop their roles as key defenders," Longmire said.

"I've been really excited by what I've seen from Gary Rohan and Byron Sumner and a number of these other younger players that are coming into our back six and what they can do as well.

"It has given those players enormous opportunities to develop and given us more depth in our back six."

A premiership player, dual All-Australian and International Rules representative, Bolton had been close to coming back from his Achilles injury before his devastating ankle injury.

"I was confident of playing in the next few weeks, so from that point of view it was pretty disappointing to happen at this stage and a bit of a shock really," Bolton said.

"One of the hardest things is I think the prospects for this year are so exciting,

"John (Longmire) has just really brought a new enthusiasm and drive to the group and we've obviously got some really talented young players coming through and I was so looking forward to getting back on the field and playing with these guys."

Longmire rated Bolton a wonderful leader and lauded the retiring defender's ability to negate both small and tall forwards.

"Very few players in the competition have been able to play on a 174cm Jeff Farmer and a 195cm Matty Richardson and still have the same level of success," Longmire said.

Bolton relished the responsibility of marking the great forwards of the current era.

"Matty Richardson, I never really enjoyed much lining up on him, because I was only up to his elbow and he could run like the wind," Bolton said.

"And James Hird is another one that springs to mind, he was always a really tough opponent.

"I really loved when (former coach Paul Roos) Roosy would say 'you've got (Lance) Franklin this week' or 'you've got (Jonathan) Brown' or 'you've got Richardson'.

"You're first thoughts are 'geez', but then after that it becomes a really good challenge."

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