All Ireland SFC semi-final/Derry v Kerry: In successive weeks over three months ago Kerry beat Galway to win the National Football League and seven days later Derry were whipped by Tyrone in the Ulster championship.

To contemplate back then the two counties in the same Bank of Ireland All-Ireland football semi-final would have required chemical assistance.

Not alone has it come to pass but Derry are regarded as a definite threat to the All-Ireland favourites. Mickey Moran's side have recovered well and exploited a useful draw to defeat testing, but not elite, opposition and have momentum.

Kerry, on the other hand, have stuttered their way this far, producing what they needed to defeat opponents of roughly equivalent standard to Derry's. The biggest source of hope for the Ulster side is Kerry's injury woes.

The absence of Séamus Moynihan may be a deficiency the team has had to cope with, but it remains a major loss.

Losing your most valuable player is bad enough, but the spectre of the second most valuable also being ruled out would have been sufficiently catastrophic to make the match an evens call.

Although named in the starting line-up, Colm Cooper will have to pass a fitness test before playing.

Hamstring injuries by their nature are treacherous and it may be that until his first sprint for a ball, neither Cooper nor Jack O'Connor nor anyone else will be any the wiser about his ability to see out the match. Against Dublin, the player was in fine form but at times subdued by the poor supply from centrefield.

Kerry look stronger there tomorrow with the return of William Kirby, who showed a keen enthusiasm when coming on as a replacement. Paddy Kelly's running game didn't suit the need for early ball and Kirby's combination with Darragh Ó Sé looks better suited both to cater for the forwards and to cope with the less experienced opposition pairing.

Derry have gone for the same starting 15 that began against Westmeath and although Moran's preference for a settled selection makes this predictable there are some raised eyebrows at the continuing failure of some replacements to break into the team.

The two most impressive aspects of Derry's quarter-final win were, one, the polish of Paddy Bradley and Enda Muldoon up front and the way they punched a hitherto highly-regarded defence full of holes and, two, the gumption displayed as soon the match turned against them in the second half.

For most observers, the moment at which Westmeath finally hit the front after a litany of wides and with less than 10 minutes to go was the moment Derry should have folded, but instead they bounced back and regained the initiative, leaving the Leinster champions stunned.

Yet, the replacements were so integral to that response from Eamon Burke's equalising score to Conleth Gilligan's hard work that a change or two would have been justified.

Kerry manager Jack O'Connor hasn't shown any such reticence after the lack-lustre tussle with Dublin and the headline change saw Michael Russell dropped. Given his form the omission wasn't a major surprise in Kerry.

The hope will be that he'll be sufficiently affronted by the demotion to root out his best game and that if Cooper's hamstring goes ping, the Killorglin forward will prove himself an impressive reserve.

The alteration leaves Kerry looking more balanced with a physically imposing half-forward line and their scorers on the inside. This entails Declan O'Sullivan refocusing his game from wandering out the field to finishing closer to goal and Eoin Brosnan in the optimum position to run at the Derry defence.

Niall McCusker's vulnerable pace won't be threatened by Dara Ó Cinnéide and the full back will be comfortable following the Kerry captain out deep.

Should it start to go wrong, Ger O'Kane will be swiftly introduced.

There is much to admire in Derry's rehabilitation.

Aside from the goals and spirit in the quarter-final there was the sharpness of the half backs - with Francis McEldowney excellent and happily recovered from injury this week - on breaking ball and the calm distribution but this is a major step up for the team.

Kerry have won the league and the Munster title, neither in themselves guarantees of an All-Ireland, but signs that the team has delivered when it was needed.

In adversity Kerry have dug deep and twice had to claw back big Limerick leads. In addition, most of the players have at least one senior All-Ireland medal.

That's a level of big-match experience that Derry are only starting to compile.

Experience added to class and resilience looks a decisive combination.