If a team in Gaelic football isn't constantly evolving, no matter how good, they’ll eventually be exposed.

What has happened in Kerry and Tyrone over the past four years has been less evolution and more revolution.

These modern rivals last met at the All-Ireland semi-final stage in 2015 when the Kingdom came out on top by 0-18 to 1-11 in the gloom of a Croke Park battered by heavy rain.

Kerry were defending champions at the time and went on to lose the final to Dublin a few weeks later, the start of the Boys in Blue's current four in-a-row.

Éamonn Fitzmaurice didn’t start the rebuild immediately after this match, some would say he left it too long, though new manager Peter Keane started this year with a very different panel of players.

Kerry manager Peter Keane

Tyrone were in a period of transition, the outfit that won three All-Irelands the previous decade had finally broken up and manager Mickey Harte was trying to piece together a new team to reach the summit with.

For the Kingdom as few as four of the players that started against the Red Hand County four years ago might line out for throw-in this weekend.

Starters in 2015, Brendan Kealy, Marc Ó Sé, Anthony Maher, Johnny Buckley, Donnchadh Walsh, Colm Cooper and Kieran Donagh have all retired, as have Fionn Fitzgerald, Bryan Sheehan, Darran O’Sullivan, and Aidan O’Mahony, who all came on as substitutes.

Peter Crowley is sidelined with injury this season, Jonathan Lyne and Killian Young start mainly on the bench and 2014 Footballer of the Year James O’Donoghue has seen his game-time curbed by injury and loss of form.

In their place have come members of the county’s five in-a-row All-Ireland minor winning teams, prodigious young talents like Tadhg Morley, Tom O’Sullivan, Adrian Spillane, Gavin White, Seán O’Shea and David Clifford.

Cathal McShane and Tyrone manager Mickey Harte

For Tyrone, Aidan McCrory, Cathal McCarron, Ronan McNabb, Justin McMahon, Mark Bradley and Seán Cavanagh have all departed the scene while Darren McCurry departed and has since returned. That’s half a team.

In their place Harte has leaned heavily on the side that won the 2015 All-Ireland Under-21 final,a spicy affair against Tipperary at Parnell Park.

Padriag Hampsey, Kieran McGeary, Frank Burns, Conor Meyler and Cathal McShane have all graduated from that set-up; McShane in particular becoming a central pillar of Tyrone’s attacking game plan.

Tyrone are one game away from their second All-Ireland final appearance on the bounce while many rate Kerry as Dublin’s closest competitors this year and the team with the best chance of dropping the Dubs’ drive for five.

The radical surgery on both sides has worked and in Sunday’s All-Ireland semi-final we will see which county has been most successful with their refit.

Kerry are one of just two unbeaten teams left in the competition, along with Dublin, who take on Mayo in their semi-final on Saturday.

Tyrone have recovered brilliantly from their Ulster semi-final defeat to Donegal and their weekend defeat to the Dubs can be discounted as Harte fielded a second-string side with both eyes already on the Kingdom clash.

Darren McCurry and Shane Enright in 2015 - both should feature on Sunday

Sunday 23 August, 2015
All-Ireland SFC semi-final
At Croke Park

Kerry 0-18
Tyrone 1-11

Kerry: Brendan Kealy; Paul Murphy, Marc Ó Sé, Shane Enright; Jonathan Lyne, Peter Crowley, Killian Young; David Moran, Anthony Maher (0-01); Stephen O'Brien (0-02), Johnny Buckley (0-03), Donnchadh Walsh (0-01); Colm Cooper (0-02), Kieran Donaghy (0-01), James O'Donoghue (0-04). 
Subs: Fionn Fitzgerald for Ó Sé (black card), Paul Geaney (0-03) for Donaghy, Bryan Sheehan for Moran, Darran O'Sullivan for O'Brien, Aidan O'Mahony for Crowley, Barry John Keane (0-01) for Walsh.

Tyrone: Niall Morgan (0-01); Aidan McCrory, Ronan McNamee, Cathal McCarron; Ronan McNabb (0-01), Justin McMahon, Peter Harte (1-00); Colm Cavanagh (0-01), Mattie Donnelly (0-1); Tiernan McCann, Mark Bradley (0-02), Conor Meyler; Darren McCurry (0-03), Sean Cavanagh, Conor McAliskey (0-02).
Subs: Padraig McNulty for Meyler, Conor Clarke for McNamee (black card), Barry Tierney for McCrory, Ronan O’Neill for McCurry.

Referee: Maurice Deegan.