Triple All-Star winner Keith Higgins is unlikely to recover in time to help save Mayo's top-flight status on Sunday.
Manager Stephen Rochford doesn't expect to have the Ballyhaunis clubman for the crucial relegation clash with Down in Castlebar.
Rochford is going to be without full-back Ger Cafferkey, who was yesterday ruled out with a hamstring injury, but hopes of having the versatile Higgins back for Sunday are fading.
Higgins is also troubled by a hamstring problem, having being injured while playing at centre-forward against Donegal.
"Keith has been making a good recovery from his hamstring injury, but Sunday might just be a week too early for him. We will monitor it very closely throughout the week but, at this stage, it looks like he will need more time."
Cafferkey has been ruled out having been injured in Sunday's 1-11 to 1-7 win over neighbours Roscommon, while Rochford is hoping that his five U-21 players - Diarmuid O'Connor, Stephen Coen, Conor Loftus, Michael Hall and David Kenny - will come through Saturday evening's Connacht final against Roscommon.
Kevin Keane could return to defence in Cafferkey's absence as Mayo, the team with the longest stay in Division 1, look for the win which should ensure their top-flight status.
Donal Vaughan, who has been struggling with a calf injury for the past few weeks, was taken off at half-time on Sunday against Roscommon and will be monitored during the week.
"Sunday is a very big game for us," added Rochford. "Down will be very keen to end their league campaign on a high note and we simply must win. There are a lot of permutations at that bottom end of the table, but we can only try to control what is within our grasp, and that means our sole focus is on beating Down and hoping that that will be good enough to avoid relegation."