Mayo and Donegal, plus the danger of the unknown, pose the biggest threat to Dublin's ambitions to become the first county in either football or hurling to complete the five-in-a-row, according to Joe Kernan.
The former Crossmaglen and Armagh manager is backing Mayo and Donegal to reach the semi-finals from Group 1, which also features Kerry and Meath, with Dublin and Tyrone emerging from Group 2 ahead of Roscommon and Cork.
"I would rank it Dublin, Donegal, Mayo and Tyrone in terms of the All-Ireland. If Kerry lose to Mayo next Sunday, they're in trouble. It's a huge game for them. They got an eye-opener against Cork, who caused their defence all sorts of problems in the Munster final. Can they fix it so quickly? You'd have your doubts," he said.
Kernan has been impressed by Donegal's rate of development and Mayo's recovery talents, which, once again, have steered them to the business end of the Championship despite losing in Connacht.
"The Mayo defence is always pretty solid and they have a few new forwards, who are showing well. Cillian O'Connor's return is a big boost and Darren Coen has been excellent.
"Obviously they need Lee Keegan at full fitness, but it they get everyone right, they'll take beating.
"There's a lovely balance about Donegal. They have strength, pace and mobility throughout the team, as well as a lot of brilliant individuals. Jamie Brennan has been excellent in attack.
As for Dublin and the five-in-a-row, Kernan suspects that factors as yet unknown could play a part.
"At face value it's theirs to lose, but things can change. They haven't had injury issues with key players in previous years. It might be the same again, but you never know.
"Kerry were odds-on to beat Offaly in 1982, but were caught on the day. It could happen to Dublin too. There's still a long way to go in this Championship," he added.