Mayo’s Rachel Kearns could be sidelined for the rest of the AFLW season due to a shoulder injury sustained in Geelong Cats' opening game of the campaign.

Kearns, a two-time All-Star who also played soccer for Galway, had to go off in the first quarter of her team's win against Richmond following a heavy challenge from Beth Lynch at the weekend.

"Rachel underwent surgical repair of her AC joint this morning," said head AFLW physio Erin Nelson.

"This will most likely be a season-ending injury."

It's a desperately unlucky blow for Kearns, who headed Down Under a year ago.