Mayo's prospects of reaching the League final next month, and perhaps laying the big-day bogey which has afflicted them for so long to rest, are all but over after having two points snatched from what they thought was safe-keeping in MacHale Park yesterday.
They were the hottest of favourites to provide Cavan with another lesson on the difficulties of life in Division 1 but after doing so for much of the first half, the mood and tempo changed dramatically just before the interval.
From trailing by 0-9 to 0-4 just past the half-hour mark, Cavan stung Mayo on the run-in to the break, hitting them for 1-1 in a quick-fire smash and grab which almost certainly was the tie-breaker.
Gearoid McKiernan, who had earlier struck two frees, added a point before pouncing for the crucial goal in the last act of the first half.
Having played against the wind, Cavan had a real pep in their step as they headed for the dressing-rooms and were even more energised when they re-emerged for the second half. Mayo, in contrast, were deflated by the rapid turnaround and while they were first to score in the second half, the momentum quickly swung Cavan's way.
"That goal was very important. If we had gone in even four points ahead, we would have asked different questions of Cavan in the second half," said Mayo manager Stephen Rochford. Instead it was Cavan who raised the bigger queries.
Their tactic of flooding the defence - often with 12 or 13 players - wasn't exactly easy on the eye but that facet of their play came when they counter-attacked at speed.
They found it surprisingly easy to make progress down the middle and once their accuracy levels - they shot eight wides in the first half - improved Mayo were stretched to breaking point.
Four unanswered points between the 38th and 44th minutes gave Cavan the lead for the first time and sent their confidence soaring.
They extended the lead to two points and while Mayo rallied with excellent points from Danny Kirby and Lee Keegan (2) to lead after 58 minutes, they failed to score again.
However, Cavan were far from finished and added three points in the final 10 minutes, steering them to a victory that greatly increases their chances of survival in the top flight.
Their remaining two games are against Kerry and Roscommon, challenges which they will be looking forward to with renewed optimism that would not have been the case had they suffered defeat yesterday.
"We proved today that we have the ability to do well in this division when we perform. Now we need to get more consistency into our performances," said Dara McVeety, who in addition to scoring three points was involved in much of Cavan's more creative play.
McKiernan was a real powerhouse around midfield while Rory Dunne, Killian Clarke and Tomas Corr were also hugely influential in taking the challenge to Mayo.
It was a very satisfying occasion for new Cavan manager, Mattie McGleenan, who has talked for months about the potential in his squad.
They had not delivered on it in previous games but once they realised that Mayo were vulnerable, they powered forward with real ambition and purpose.
"The pleasing thing was the team turned up in its entirety and played to their ability. And then we have some outstanding individual performances on top of that. We need that all the time. Hopefully this is the start," said McGleenan.
Mayo made it easier than it should have been but there was still a lot to admire about Cavan's structure and application. Even against the wind, they created some excellent chances but were let down by wayward shooting.
McVeety believed the conditions were largely responsible for the inaccuracy but it was different in the second half when Cavan had the wind behind them.
"We were able to shoot from further out and we got a few points that way," he said.
Rochford accepted that even if Mayo win their remaining two games, it's highly unlikely they can reach the final. At the other end of the scale, the haunting spectre of relegation is now unquestionably on the horizon, with games against Tyrone (away) and Donegal (home) to come.
Of course, Mayo were in a worse position this time last year, having won only one of five games before picking up four more points en route to safety.
Still, while the current predicament will be of concern to Mayo supporters after watching the side flop so dismally against Dublin and squander a five-point lead against the Breffni, some positives did emerge yesterday.
Midfielder Kirby led the way on that front, emerging as top scorer with four points, all kicked in open play, some from very acute angles. Andy Moran continues to be Mayo's most consistent forward, scoring 0-3 amid heavy blue traffic.
"We did well enough in the first half - eight points from open play was a good return against a stubborn defence but the goal gave Cavan impetus and we were on the back foot a fair bit in the second half. They made it very hard for us, " Rochford added.
Scorers: Cavan: GMcKiernan 1-5 (3f), D McVeety 0-3, T Corr 0-2, R Dunne, C Madden, M Reilly, J McCutcheon 0-1 each.
Mayo: D Kirby 0-4, A Moran 0-3, L Keegan, C O'Shea 0-2 each, T Parsons, F Boland, K McLoughlin (f), S Nally 0-1 each.
Cavan: R Galligan 6: F Reilly 6, R Dunne 7, K Brady 6; N Murray 6, K Clarke 7, C Moynagh 6; G McKiernan 9, T Corr 8; M Reilly 7, D McVeety 8, N Clerkin 6; G Smith 6, C Madden 7, S Johnston 5.
Subs: C Mackey 6 for Johnston (45), C Brady 6 for Clerkin (61), J McCutcheon 7 for Madden (62), P O'Connor for Corr (71).
Mayo: D Clarke 7; B Harrison 6, K Higgins 6, P Durcan 7; C Boyle 6, L Keegan 7, D Vaughan 5; T Parsons 6, D Kirby 8; F Boland 6, C O'Connor 5, C O'Shea 7; K McLoughlin 5, A Moran 8, C Loftus 7.
Subs: S Coen 6 for Vaughan (53), S Nally 6 for Boland (55), E Regan 5 for Loftus (61), N Douglas for O'Shea (66).
Ref - A Nolan (Wicklow)