Mayo are set to be without star forward Cillian O'Connor for this year's Championship after he suffered an Achilles Tendon injury in the Westerners' Allianz Division 2 league semi-final win over Clare.
The Championship's all-time leading scorer limped off the pitch in Ennis last Sunday and Mayo have now confirmed that he will undergo surgery this week.
They said in a short statement: "Following last Sunday's NFL game versus Clare GAA all injured players received further assessment with the Mayo medical team.
"Cillian O’Connor sustained an Achilles Tendon injury that will require a procedure this week.
"We wish him well and look forward to seeing him on the playing field again as soon as possible."
Mayo begin their Championship campaign against Sligo on Saturday week and the news will come as a huge blow to manager James Horan.
