Sydney coach John Longmire has revealed forward Tom Papley played through broken ribs during the early portion of the year, stating 'no one knew' about it.

The Swans defeated the Western Bulldogs by two points in a Thursday night thriller at the SCG, as Sydney was aided by Papley's four majors on the night, which also happened to be his 27th birthday.

Speaking to the media post-game, Longmire started by stating Papley has had 'some challenges' this season, eventually going on to reveal his forward's secret injury.

"He's had some challenges this year," Longmire started on Thursday.

"He broke his ribs at the start of the year, and no one probably knew about it, well no-one did know about it. And it was lingering for quite a while, then a number of other injuries that he's had meant that he hasn't been able to train.

"So, he's just had a tough year to try and physically get up to be able to train to perform well."

Despite the supposed early-season ailment, it hasn't stopped the dangerous goalsneak from playing in every Swans game this season, going at an average of 1.8 goals per game, which currently represents the second-best campaign average of his career.

While Papley celebrated his milestone day with a handful of goals and a victory, his coach, Longmire, did too, coaching the Swans to a win in his 300th matchday on Thursday evening.

Initially joking about the 'carry-on' associated with such a prestigious achievement, the veteran Sydney mentor didn't want to be 'flippant' about what the milestone signifies.

"It's a bit of carry-on, isn't it?" Longmire initially jested.

"I had a cake yesterday, that was a bit of carry-on, got my big boofhead on the big screen, so that was a bit of carry-on.

"But I don't want to be flippant about it, I'm very lucky to work for a fantastic footy club and those boys tonight. I've seen all their tapes as young kids coming through, from the youngest ones who were just drafted to the oldest ones … I've been fortunate that I've been part of a lot of their journeys.

"I feel very privileged and honoured that I was a part of it for so long, for so many of them."

By emerging victorious on Thursday, the 11th-placed Swans kept their fading finals hopes alive, as they prepare for a Round 19 matchup with Fremantle in Perth.