Heeney suffered the setback while training on Monday and will undergo surgery on Thursday.

The 23-year-old will need to wear a brace and avoid contact for a month following the operation but, barring any setback, he won't be in any danger of missing the Swans' season-opening clash with Adelaide on March 21.

Franklin, who underwent knee surgery earlier this month, will be racing the clock to prove his fitness for round one.

Not all broken thumbs require surgery but Swans football manager Charlie Gardiner noted in this case that surgery was unavoidable.

"Isaac was struck awkwardly on the hand in a fairly routine contest during training. It was just one of those unfortunate incidents that can happen at training," Gardiner said.

"Scans confirmed a fracture in his thumb.

"Isaac is obviously disappointed but he should be back running in a matter of days and we're confident he will be available for the start of the season."

Heeney's latest setback comes after he managed a troublesome ankle injury throughout the Swans' 2019 campaign, when they missed finals for the first time since 2009.

The broken thumb will force Heeney to miss the bushfire relief match at Melbourne's Marvel Stadium on February 28, when Victoria will face an All-Stars team to help raise funds.

Heeney, who was holidaying at Manyana on the NSW south coast with teammate Luke Parker when they had to evacuate because of nearby fires, recently spoke of his desire to be part of the game.

"It's a massive thing for the AFL to help out where we can. I'd love to play and raise as much awareness as possible and funds," he told News Corp Australia.

"It's been devastating and I really feel for these people."

Australian Associated Press