Swann has decided that, at the age of 34 and after just seven wickets costing 80 runs each in England's three defeats here, he can no longer reach the standards he has set.
As England lost the Ashes in Perth, where Australia took an unassailable 3-0 lead, the over which has turned out to be Swann's last was dispatched for 22 runs by a rampant Shane Watson.
Even so, Australia coach Darren Lehmann was taken aback to hear the England off-spinner has called time on his outstanding career.
"It was a bit of a surprise," he said, on his arrival in Melbourne for the Boxing Day Test.
"He's been a great cricketer for England over many years, so I wish him all the best in retirement.
"It's mid-tour - I don't know what's going on - but obviously he's decided he's had enough.
"So congratulations on a great career - he'll go home as one of the England greats.
"Obviously he feels the time is right, and that's his decision."
Swann's rationale is that he is simply not able to bowl as he used to, and needs to.
He has been a victim of Australia's aggressive tactics with the bat this winter, and has not been helped either by an absence of competitive first-innings scores by England - which has made all their bowlers especially vulnerable second time round.
"If senior players can't contribute how they like, that would be their decision," added Lehmann.
"It's always tough mid-tour, but he's been a great bowler for England and has decided enough is enough and to move forward in his life.
"England are obviously going to go down the Monty Panesar path for the next two Tests, so it is a challenge for our blokes to change the way we play against left-arm spin."
Australia tried to take the attack to Swann in England last summer too, but were never able to do so consistently and ended up losing the Ashes 3-0 back then.
"We had a plan for him in England and did not execute it as well," said Lehmann.
"We changed things round a little bit here.
"Swann's a big player when they only have four bowlers, five when they have (all-rounder Ben) Stokes in their side, so you have to try to take one or two of them out of the equation.
"That makes their quicks bowl more - it was certainly a plan from us.
"Putting miles in legs of opposition quick bowlers is definitely a plan - make them bowl as much as we can.
"It means we are batting well.
"In a long series, (you) have to do that."