It's hard to think of two more contrasting teams than Offaly and Mayo who contest tomorrow's Bank of Ireland All-Ireland football semi-final at Croke Park. The Connacht champions were beaten by a point in last year's final replay, whereas their opponents have come from nowhere (worse, Division Four) with a largely dismal championship record stretching back to the county's previous provincial success 15 years ago.

There are other contrasts: Offaly have a settled side, forged as a unit over six championship matches of steadily increasing tempo; Mayo are instituting major tactical and personnel changes after a messy provincial campaign. The Leinster final was proclaimed (with maybe a nod in the direction of hyperbole) as the rebirth of football; Connacht's decider was dreadful and Mayo haven't played well - or been obliged to - for three months.

Last week Offaly players were freely available at their designated press night and appeared cheerfully relaxed whereas, a night later, Mayo's equivalent degenerated into a paranoid farce as manager John Maughan protested his team's openness while his players slunk out the back door.

Nearly all of these indicators may point in the direction of an Offaly victory, but inevitably it's not as simple as that. Last week's semi-final illustrates as much. Too much emphasis (in these pages anyway) was placed on Cavan's Ulster victory and not enough on Kerry's experience last year.

Some of those question marks are applicable to Offaly. As a forward display, the Leinster final was spectacular, more like a hurling match with the ball being moved quickly to the wings and players moving at pace onto some excellent long passes. It was, however, virtually a second-string Meath defence.

Further questions were raised about Offaly's defence which conceded 1-15, a total big enough to win most championship matches. Full back Larry Carroll appears to have acquired totemic significance to the team and is retained after enduring a hard time from each of the previous three full forwards he has marked.

Taking into account other matches from this year, it can also be seen that two of the high-performance lines from the last day played less impressively in the Leinster semi-final against Louth.

In fairness to Offaly, perspective cuts both ways and making too much out of Mayo's experience is as misleading as exaggerating the Leinster final.

That experience should have its pay-off in an ability to handle the big occasion (which Mayo demonstrated impressively in May when beating Galway in Tuam for the first time in 46 years) and the accompanying pressures. But it should also benefit a team in terms of cohesion and teamwork.

Mayo's selection appears to forfeit much of that advantage. This isn't entirely the management's fault. They have been dealt serious blows in the form of injuries to Maurice Sheridan and Kevin Cahill, whose loss at full back is particularly inopportune in the light of Roy Malone's emergence as the best full forward in the championship.

Sheridan's hamstring problem is worse news - at least Pat Holmes at stand-in full back has a track record in man-marking. The best dead-ball exponent in the country at the moment, Sheridan's problem is in his kicking leg, so questions remain regarding his effectiveness, even though he has made the cut.

Liam McHale's move to full forward has exercised minds in Mayo. Within the county, the sight of him in a number 14 jersey is generally a trigger of unhappy memories. Not alone has McHale looked uncomfortable in the position, but his isolation on the inside line robs the team of its principal dynamic from last year - his strength around the middle and his acute perceptions when carrying and distributing the ball.

His place at centrefield goes to David Heaney, who makes his full championship debut. Heaney's form is advanced as one of the reasons behind the realignment of McHale but, all in all, the gambit looks a fairly experimental move this late into a championship.

Some talk has circulated about David Nestor switching to full forward with McHale dropping to centre forward and Colm McManamon moving to the wing. This would be another radical move, but has the merit of cutting cloth to measure.

Larry Carroll's most comfortable moments are contesting high ball and if he was to focus on breaking possession away from McHale all afternoon, he would probably do alright. Nestor, on the other hand, is the sort of player - quick and elusive - against whom Carroll has been struggling.

Whereas this match, like last week's, is very hard to call because of the lack of reference points, logic points towards Offaly.

They have injury concerns, with Vinny Claffey subject to a fitness test and Ronan Mooney also doubtful for what would be a serious loss. There is also a question mark over Carroll's capacity to hold on the edge of the square, but similarly, Dermot Flanagan's lack of pace is a perpetual worry to many Mayo people.

Elsewhere at the back, the Mayo team is assured, with Ken Mortimer consistently impressing and the half backs fluent and lively.

But here again is a balance: James Nallen, who is an attacking centre back, faces the grim prospect of Sean Grennan, who is a defensive centre forward.

In conclusion, too much of the argument in favour of Mayo depends excessively on their being much better than form suggests and Offaly significantly poorer. There is truth in both assertions, but not enough to close the gap.