It was perhaps the magnitude of the second half collapse that will distress Roscommon players and supporters alike as they mull over a remarkable second 35 minutes during yesterday's Connacht football semi-final at McHale Park, Castlebar.

The sight of full back Damien Donlon being stretchered from the pitch on the half-time whistle is definitely a mitigating factor in Roscommon's collapse. The backline required serious reshuffling - three positional switches - with Enon Gavin eventually finishing at full back. The understanding with which the Roscommon defence played in the first half, allied to their dogged determination, simply evaporated in a welter of indecision and ball watching.

It is staggering to consider that the sides were locked at 0-6 at the interval, a match delicately poised. Mayo would have the benefit of the strong breeze in the second half, but even their most ardent supporters would not have envisaged the metamorphosis that occurred. The catalyst for the change was captain Kenneth Mortimer.

His positioning at centre half forward proved to be the worst kept secret in Connacht football, much to Mayo manager John Maughan's chagrin; but the decision was vindicated emphatically in that second half. Allowed greater freedom after Roscommon's interval shuffle, Mortimer provided a fulcrum for his county's attacks; his vision and distribution created bountiful opportunities for those around him.

Suddenly, from an attack that laboured to escape the shackles of a vigilant Roscommon defence - John Casey was an honourable exception during this period - Mayo were afforded the freedom of McHale Park, scoring at will.

Maurice Sheridan's accuracy with the placed ball, eight frees in a nine-point haul, exacted maximum retribution every time an increasingly ragged Roscommon defence resorted to dragging down the player in possession.

Mayo might have grabbed a couple of goals, twice through the excellent Casey - he kicked six points from play - and once when James Horan elected to fist a point rather than test Derek Thompson in the Roscommon goal.

Colm McManamon drifted in from the periphery of proceedings to take a more central role with two fine points, and left half back Noel Connelly kicked two superb, long-range points.

James Nallen enjoyed a fine game at midfield after a slow start, but Mayo's outstanding contributor on the day was left corner back Gordon Morley. Aidan Higgins and Kevin Cahill proved very effective, but Morley's was a towering performance, frequently breaking up promising Roscommon forays and always distributing the ball intelligently.

Maughan was a little bemused by the margin of victory. "I never expected us to win by that much but we played very well in the second half. I am delighted with the performance."

When asked why Mayo had been tipped to lose by many pundits, Maughan simply stated that he was unaware of media comment.

Roscommon manager Gay Sheerin offered his thoughts to a shell-shocked team in the privacy of the dressing-room, and judging by the length of time there was plenty to discuss. The losers had started so promisingly, particularly 6 ft 5 in centre half forward Fergal O'Donnell, who kicked three fine points and always offered a physically imposing challenge to Mayo.

Donlon and the Gavins, Denis and Enon, all played competently while captain Clifford McDonald and Ciaran Heneghan afforded their opponents very little room. Only Rossa O'Callaghan struggled, faced with containing the excellent Casey. By the end of the match, though, all bar Denis Gavin would flounder.

In attack, Lorcan Dowd was anonymous, Frankie Dolan and Francie Grehan marginally less so. Derek Duggan kicked one magnificent point from close to the touchline, but as the supply of ball became more scarce he was forced into a role of spectator.

Roscommon started brightly enough: backed by the breeze they scored two early points through O'Donnell and a Duggan free. Noel Connelly's surge and fine, long-range point woke up Mayo in a game that charitably could be described as scrappy. Passes were misplaced with abandon, often embarrassingly easy ones.

Still the contest remained compelling. But then came the second half revelation, and Mayo completely eclipsed their opponents. It took a while for the Mayo section of the crowd to comprehend what they were witnessing, their muted applause gradually giving way to a more ebullient backing.

All the while Roscommon heads sunk lower and lower until finally the whistle of referee Brian White brought a merciful relief to their suffering. The evidence of last year's championship suggested that Roscommon could be potential champions, but the manner of this defeat, rather than the loss itself, should prompt a serious rethink in the county.

Those who have already penned the Mayo obituary may yet find the county in rude good health.