I remember the Dublin matches at Croke Park in the middle of the last decade. Monaghan were going well at the time and had won Ulster titles in the recent past. We also competed really well with them in the league and in those years, one-score wins for either side were common.Championship was different, though. In the 2017 league, we had lost to them by three after getting caught for a late goal. A couple of months later, in the All-Ireland quarter-final, we never got going and they piled on the pain.In 2014, we had our plan in place to stifle them and we were doing just that for 25 minutes. But one slip, one mistake and Eoghan O’Gara just gets to pass it in over the top. In goes Diarmuid Connolly. Goal. Same thing happens with James McCarthy and Bernard Brogan. Goal.In six minutes, we conceded 2-3 and went from 0-3 each to goodnight. On those scoring runs, goals used to ignite Dublin and their supporters. It was at times as if the Hill was willing the ball over the line or sucking it over the bar. You could see in their play and their demeanour that they were going for your throat and it was a very difficult place to be.The point is that it’s not that Dublin who Donegal were playing last week. This Dublin had lost five of their six previous championship matches at Croke Park and manager Ger Brennan was even floating the idea of taking the team out of there and back to Parnell Park.[ Darragh Ó Sé: Dublin are on a high, but Galway have been building quietly and fear nobodyOpens in new window ]Struggling for confidence, they should have been put away by a team ranked among top contenders for the All-Ireland and I expect Galway will do that on Sunday, especially with Dublin’s injury issues. They certainly must win if they’re going to live up to expectations as, now, Kerry’s main challengers.What happened is more a question for Donegal, who signed off with three defeats in four championship games. Brendan Devenney referred to the possibility that Donegal had gone too hard and too soon in the league and didn’t have the energy for championship, and that’s what it looks like.Dublin’s Paddy Small scores his side’s second goal of Sunday's game against Donegal. Photograph: Ryan Byrne/Inpho Listening to Jim McGuinness after all three games that they lost, and he was talking about the lack of energy and running power. Donegal’s whole game plan is based around that ability to outrun you, outwork you, and turn you over.They didn’t have it against Dublin, or the necessary level of aggression and intent in their play. That’s their whole template and how and why it went wrong raises question marks over Donegal. They’re the only ones who can really provide answers.It must feel a long way from Killarney in May when they overran Kerry, but that game was in the balance at half-time before Micheál Burns was sent off. It may have been unpalatable for Jack O’Connor to take a second big beating after the league final, and in their own back yard, but he knew that there were important players to return from injury and the championship literally opened up for him last weekend.[ Kerry entered last weekend as Sam Maguire contenders. They came away as outright favouritesOpens in new window ]He must have been aware that Armagh would probably be an obstacle to his team retaining Sam Maguire but, like most others, would have assumed the contest was likely to be in Croke Park.Instead, he gets to play them in Killarney just six days after they have suffered a demoralising defeat, which left them low on self-belief and energy. You could just see the effect of the previous week on Armagh. They pressed hard to start with but looked blunt and inaccuracies mounted.It was a big contrast with the efficiencies of the team at their best, how good they were at getting inside your rearguard and taking easy scores from 20, 25 yards out.Joe O’Connor scores Kerry's third goal against Armagh last Saturday. Photograph: James Crombie/Inpho They didn’t seem to have that same drive or pace to put those runners into pockets of space, and as a result started taking pot shots that we wouldn’t have associated with them two months ago.Kieran McGeeney said he didn’t feel the six-day turnaround contributed to missed chances, but I think in a way it did because their reduced energy levels caused them to try things that they weren’t usually doing earlier in the year.The problems had started in the Louth match. That’s why they were vulnerable to the late goal. Joe McElroy went on to his left foot at one stage and Tomás McCormack put one on his left foot, shots that ordinarily they weren’t taking. Until then, it had been about working it, moving it, holding it, popping it in and then the opportunity would come.That slippage continued in Killarney and the general carelessness was the major cause of the killer goal just before half-time.Kerry were clinical and got players back from injury. Only Tom O’Sullivan has yet to return.O’Connor is where he wants to be, heading to Croke Park with nearly a full deck of cards and in glorious weather. He has held his nerve and wasn’t tempted to hurry players back when Donegal came to town. In two days last weekend, he watched as both of his team’s closest rivals ran out of battery.Last year I made the point that despite not having been previously prolific with the two-pointers, Kerry had the best footballers on the best pitch in the best conditions. What did people think was going to happen?Tyrone have a great future with some fine young players like Ronan Cassidy and undoubtedly they can trouble their opponents on Saturday, but in current form Kerry can hurt anyone.