DUBLIN v DONEGAL: GAVIN CUMMISKEYon the match-up of Michael Murphy and Rory O'Carroll, a key part of Sunday's tactical battle

RORY O’CARROLL and Michael Murphy have met before. Fifteen months ago they became entangled in a captivating duel in the All-Ireland under-21 football final. Dublin won by two points but only after Murphy slammed an injury-time penalty against the crossbar.

That ball still needed to drop to earth. It was O’Carroll’s fist that punched it to safety as Murphy’s big frame sank on to the turf. The rivalry between two of football’s best young players will be reignited in Sunday’s All-Ireland semi-final.

The general expectation before last year’s game in Breffni Park was that Murphy’s power would tip the scales in Donegal’s favour. In the opening seconds of that game he charged towards the Dublin goal only to be stalled by O’Carroll’s shoulder.

Donegal proceeded to rain high balls down on the pair, but O’Carroll either broke them to a fellow blue shirt or took clean possession himself. He was perhaps fortunate not to be yellow-carded for an early jersey tug; it was Murphy’s frustration that eventually betrayed him when he tripped his marker on 47 minutes.

“They did have a mighty tussle,” said Jim Gavin, the Dublin under-21 manager and part of the 1995 All-Ireland winning side. “Rory was man of the match and had an outstanding game for us but Murphy played very well too. He gave us an awful lot of trouble during the game.

“Michael would be well known to a lot of the Dublin guys who have played out in DCU. But yes, what swung it for us that day was Rory’s composure. He is very good under the high ball but is also a very astute reader of the game.”

When Murphy drifted out to centre forward, O’Carroll followed but Gavin does not see the Dublin full back leaving his post on Sunday. “People say Dublin play a zonal defence but the six defenders just hold their shape. They go man to man, passing markers off to each other. They play an orthodox back six.

“In the 2010 All-Ireland final we released our two wing backs to support our forward line because of Jim McGuinness’s tactics. He pulls 12 Donegal players back into defence. But our full back line and centre back (who was James McCarthy) kept that diamond shape. It would be interesting to see if Pat Gilroy will release (Kevin) Nolan or McCarthy to attack up the flanks on Sunday.”

Gavin slips into tactical mode for the rest of the conversation – because that is what every game against this solidly structured Donegal team comes down to.

“I was very disappointed in Tyrone in terms of how they set themselves out defensively. Harte probably thought he would keep it tight and then empty his bench in the last quarter but by that stage Dublin had all the momentum.

“On Sunday it will be a completely different game for the Dublin forwards. The saturation in the Donegal defence will be at a different level to what they experienced against, say, Wexford.

“Players have to be patient on the ball but that’s not to the extent of labouring the attacks. They need to push the ball on at pace and try to penetrate. One of the ways you do that is you stretch the defence by switching the attack. So, if you are going down one channel and that is blocked you’ve got to get the ball quickly across the pitch.”

Paul Flynn and Bryan Cullen have proven themselves capable of switching the point of attack with a 40-yard foot pass.

“There is plenty of space left in Croke Park to switch to the blind if one side is blocked up. If you try to go down the middle (Karl) Lacey is playing quite well there with (Neil) Gallagher and (Rory) Kavanagh dropping back into that centre pocket. Two of the Donegal half backs are dropped into the full back line. Dublin’s best option is down the flanks.”

Gavin sees Dublin winning with a few points to spare. He sees O’Carroll and the Dublin defence holding firm thereby turning matters into a shooting contest.

“Man for man, if Dublin are patient and control the game, we could win comfortably in the end. I don’t know if Colm McFadden has the pace to break down this young Dublin defence. Murphy will probably drift out from full forward, but otherwise it is hard to see where the rest of scores will come from. I can’t see them getting over the magical 17-point championship mark, maybe only about 10 points.”

Not that Diarmuid Connolly and the Brogans will have such clean sights of goal this time around.

“Connolly won’t be getting the freedom to pick up ball inside the 25-yard line, like he did against Tyrone. We’re going to have to get our scores from somewhere else. But we have plenty of good shooters there, certainly in comparison to Donegal.”