All-Ireland SFC semi-final: Keith Duggan discusses the Kerry and Tyrone line-ups with Martin Carney and Brian Canavan.

The decision by the Tyrone management not to disrupt Cormac McAnallen's masterful apprenticeship at full back is significant for a number of reasons. It confers upon this year's All-Ireland semi-final series the unusual distinction of four teams left in the competition without a "natural" number three.

But for the purposes of Sunday's game, it means that both teams bring to Croke Park incredibly strong reserve players. McAnallen's assured performance in an area left vulnerable by injuries to Colin Holmes and Chris Lawn means that both those players must wait in the wings for their chance.

Stephen O'Neill, an All Star two seasons ago, cannot get back into the forward line and Declan McCrossan, the flying wing back turned wing forward has also lost out. Last year against Sligo, he started the game with Owen Mulligan introduced as a substitute.

Kerry's full back conundrum has been well documented. After a winter of trials, they have been forced to play Séamus Moynihan in the square again. Elsewhere, though, they too have a formidable range of options, with former All Star Johnny Crowley leading the charge of a reserve forward line that includes Aodhán MacGearailt and Declan Quill.

"The thing is that there is no way you could tamper with the front three that dismantled Roscommon," notes football analyst Martin Carney who has watched both teams playing extensively over the summer.

"And funny enough, when I heard Tyrone were persisting with McAnallen, I immediately wondered if he would be suited to marking Declan O'Sullivan. I thought O'Sullivan was truly remarkable when Kerry just pulled away from Roscommon and I just wonder if Colin Holmes will end up coming in to do a marking job there. Because O'Sullivan's movement and availability is so good. It won't be just a question of raining in high balls for McAnallen to deal with. It will require a very sticky marker."

There have been a number of calls for the introduction of Crowley to Kerry's starting line-up.

"When I saw him come on against Roscommon, I remember saying to the person beside me that I am always amazed they don't start him," says former Armagh manager Brian Canavan.

"I feel that the Kerry full-forward line lacks a strong ball winner as they discovered to their cost in last year's final. Bringing on Crowley with just eight minutes to go that day was a bit of a blunder and if it is tight the next day, I think we can expect to see him sooner rather than later."

As Carney sees it, Tyrone have a stronger bench but precisely how they deploy it will depend on Darragh Ó Sé.

"As ever, everything from a Kerry perspective hinges on Darragh. He is the most dominant midfielder in the country and the influence he brings to bear on how Kerry operates cannot be overestimated. So even if things are fine in defence for Tyrone, Ó Sé's exertions may require them to bring McAnallen out to bring his own abilities to bear in that sector. Eoin Brosnan is a wonderful player to watch and has done well at midfield even if he is a small bit of a "heads down" player. Darragh still carries a heavy burden in terms of the standards he reaches. Of course, Kerry have the option of Donal Daly also. But that area is critical."

Canavan agrees. "Maybe because of Ó Sé's strengths, the Kerry midfield has tended to seem a bit uneven. My guess is that Mickey Harte is just hoping he doesn't have to move McAnallen out to midfield. I don't know if Eoin Brosnan will remain a midfielder for Kerry, I'm not fully sure if that is his position. It will be interesting to see how that breaks down on Sunday."

If Ó Sé remains the crucial figure in green and gold, does the same apply for Peter Canavan?

"I have watched all Tyrone's games this year and the difference in Peter's game is remarkable," says Canavan.

"He is still putting up the scores but he is practically inviting Owen Mulligan to be the go to man this year. Peter is very cagey, you don't see the runs into space that were a common part of his game a few years back. That conservatism is probably due to his age and also because Tyrone are not as reliant on him as they were in previous years."

Still, the presence of the most feared finisher in the game is bound to be a worry for the Kerry defence.

As Carney observes, John Sheehan was the county under-21 full back for the under-21 final of 1997 but despite trials for both Michael McCarthy and himself in the league, Kerry have failed to find an alternative to Moynihan.

The three bullets that Roscommon fired late in the quarter-final has left that sector of the team open to scrutiny.

"Well, what I found about Kerry is that they will always give you scoring chances," says Canavan.

"The thing is, you have to take them. Their philosophy would be a lot different to Armagh's in that they individually mark and go to win the ball. That leads to breaks and does give opportunities. I don't think that will differ greatly the next day and going forward, I expect this to be a terrific game."

Kerry's cover at the back remains much thinner than that of Tyrone. "It is remarkable, given that Kerry have provided a virtual who's-who of full backs down the year that they haven't fully resolved this situation," says Carney.

"It has been going on quite a while now. But they are lucky to have a player of Moynihan's ability to step into the role."

Strong as the 15 on both sides are, the closeness of this game and the similarly attack-minded nature of both counties means that changes are bound to occur and it could well be one of the players that starts on the bench that has the all important input.

"Overall I think Tyrone are slightly stronger in reserve," says Carney. "But that is in the context of the game. Kerry have players that can turn a game in a flash."

"I suppose for both managers the pressures of having such options is knowing precisely when and how to use them," says Canavan.