THE old order changes. This year's All Ireland football semi finals are a vindication of the under 21 championship. All four teams have recently made a sizeable impact on the top under age grade.

Tomorrow's meeting at Croke Park between Kerry and Mayo brings together the counties who fought out last year's under 21 final - and surprisingly, a large number of the personnel involved. Kerry start seven of the side that won the title last September and Mayo start four of their team (it would have been five had David Brady been fit).

Both teams have just broken through their respective provincial championships this summer, maybe a little ahead of schedule (if not for Kerry, certainly for Mayo). Accordingly, it should be a fairly well contested match.

Should. Which is where the history of these events becomes oppressively relevant. Galway may have raised the morale of Connacht counties with their performance against Tyrone last year, but western teams have in the last 13 years managed one championship win in Croke Park Mayo's against Tyrone in 1989.

In the years since then, the county which could claim Connacht's best record at All Ireland level in the 1980s has endured a couple of grim outings in Dublin, most recently the 20 point battering from Cork three years ago.

Three factors distance Mayo from such trauma. One has been mentioned that Kerry have as little experience of the big time as Mayo. Secondly, the standards in Munster and Connacht are converging - probably more to the former's concern than the latter's gratification.

The third factor is Mayo's manager John Maughan. The fact that he guided Clare past Kerry in memorable fashion four years ago may constitute motivation for Kerry but it shows the Mayoman's facility with thin enough resources and Clare's display against Dublin in the 1992 All Ireland semi final showed his ability to prepare teams for daunting occasions.

After that match, one of the Dublin selectors expressed surprise at Clare's resilience and the difficulty Dublin had in putting them away.

Kerry have taken only one major scalp, Cork's. But that was all the draw allowed them to do. In the Munster final, they left it late but the self belief exhibited in those closing minutes was ample testimony to the changed relationship with Cork.

Issue has been taken with some elements of the selection. The winning end game in Cork was with a radically changed line up to that which started. Sean Burke's injury may have forced Kerry's hand but they looked more potent with Seamus Moynihan at centre back, Maurice Fitzgerald at midfield, Liam Hassett at centre forward and Dara O Cinneide at full forward.

An argument can be made about whether O Cinneide is better on the square or in the corner - and there are no hard preferences here - but the supply of ball is the main concern in either case. When he gets it he's hard to handle, and he took three points off Mark O'Connor on an afternoon when some observers decided - and not invalidly - to give the Cork captain `Man of the Match'.

Midfield raises a couple of questions. Firstly, how quickly will Fitzgerald move there and secondly, how badly will Mayo suffer from the absence of David Brady.

At training, Brady never raised enough of a gallop even to be tested fully. Naming Pat Fallon in his place seemed, however, something of a psychological gamble. By allowing Brady four fill days to recover without the pressure of an AN Other place hanging over him, the hope would be that he could be fit to sit on the bench and be introduced if matters took a turn for the worse. The complementary talking up of Fallon and the decision to pick him as early as Tuesday had the appearances of an attempt to limit any damage to morale.

Mayo need a good return from this sector. Liam McHale was the dominant influence against Galway but he is fully complemented by Brady's physical presence and athleticism which allows McHale scope for high fielding, carrying the ball and distributing up front. How he gets on with Fallon poses questions for Mayo.

Kerry don't need as much from midfield but will want more productivity from Dara O Se, who will presumably have the task of disrupting McHale. O Se and Moynihan did a fine job on Cork's Danny Culloty and Liam Honohan in the National Football League quarter final in March and will see that rather than the limpish Munster final as their headline. Any problems will signal the arrival of Fitzgerald, whose authoritative cameo in the centre was a crucial part of the Munster final victory.

Speculation has surrounded the Mayo attack, which hasn't been settled this summer. During Tuesday's training match, both P J Loftus, scorer of three goals in a challenge against Kerry last month, and Kevin O'Neill, an All Star three years ago, threw the right shapes but it was David Nestor, the elusive corner forward who got two goals in last year's drawn under 21 final and who played on UCD's successful Sigerson Cup team this year, who received the call up. Ironically, his UCD teammate, veteran Anthony Finnerty, was dropped to accommodate Nestor.

In the other corner Ray Dempsey could count himself fortunate on the evidence of the session. He blew several goal chances and at one stage petulantly tried to trip up a defender moving out for a restart. Deciding between him and Finnerty must have been close, but Dempsey was involved in all three of the Connacht final goals.

Mayo's attack contains only one forward currently on top of his game, John Casey at full forward. Dempsey and Nestor may or may not produce and Colm McMenamon at centre forward will be deployed so deep that he will scarcely count as part of the forward unit. His absence will create space for Casey, who promises a lively afternoon for Mike Hassett, who has yet to present convincing credentials at full back.

Against Waterford, Anthony Fitzgerald gave him problems and on Colin Corkery, he was in trouble but was baled out by the Corkman's inability to do much with the ball. Sean Burke continues to look a better option at fullback, and a swap with Hassett may be on the cards.

In prospect, this match looks tipped towards Kerry. Mayo's advantage at midfield has been mitigated by Brady's injury and their defence which is solid and balanced will have to work hard on Kerry's attack which has three top class performers in O Cinneide, Fitzgerald and captain Billy O'Shea, whose energetic displays on the half forward line have been supplemented by improved score taking.

Mayo have less certain assets in attack. They can't be discounted as Maughan can be relied on to make the best out of his hand. But Kerry have better cards.