Kurt Tippett's retirement was sudden but came as no shock to Sydney coach John Longmire.

Tippett ended his 178-game career on Monday after deciding he would be unable to get back to peak physical condition from an off-season ankle reconstruction.

The 30-year-old battled through last year after first suffering an ankle injury against the Western Bulldogs at Etihad Stadium in round two, and never fully got over the issue.

His decision may have surprised the footy world, given the ruckman had three years left on his contract and the Swans were expecting him to be running after the Christmas break, but Longmire said he wasn't blindsided when Tippett told him he wouldn't play on in 2018.

"We understood it was on the radar at the end of last year," he said on Tuesday.

"It's a big decision for anyone to make and we knew once he had the ankle reconstruction that it was going to be a big challenge to go through the whole rehab process again to get back and play.

"You underestimate the mental challenges you have when you do that year on year and he's had a few of those over the journey.

"People don't understand how tough it was for him last year, he hurt his ankle in round two and had to play the whole season under pretty severe duress."

Tippett's untimely exit just weeks before the start of the new season leaves the Swans one player short this year, with Sam Naismith, Callum Sinclair and Darcy Cameron the only three recognised ruckmen on the senior list.

Athletic youngster Joel Amartey was added to the club's rookie list at the end of last season and looks to have a bright future, but he will need time to develop at NEAFL level.

Longmire said he had no issue with the timing of Tippett's retirement despite the problems it could cause his club later in the season.

"It's a very hard thing to put a timeline on these decisions, it's a little more complicated than that, and you have to get to that decision in your own mind," he said.

"It's a tough life-call to make for a player to retire and it does take time.

"Once that decision is made he felt comfortable with it and we as a club felt comfortable with it as well."