Two weeks ago the Irish hinted at their potential by dispatching second favourites Australia, but yesterday's demolition of the Azzurri in a do-or-die showdown at Otago Stadium was even more telling.
Knowing that defeat would see them return home today, Ireland produced a highly clinical display that swept them into the quarter-finals as Pool C winners.
Kearney believes their unbeaten march into the knockout stages has sent out a message to their World Cup rivals.
"We had that great win against Australia, but there were still a lot of doubters out there," said the Lions full-back.
"This was a big day for Irish rugby, our personalities, us as a team and how we want to be perceived as a team.
"Obviously there was a quarter-final place at stake and that's massive, but in terms of building a legacy and how this Ireland teams wants to be known, beating Italy was quite important.
"We finished top of the pool and are slowly creating something really special. We feel as if there's more to come.
"I hope we're perceived to a be a tough team to play against that's building and improving with every game.
"That's four wins out of four, so we have sent out bit of a message.
"Any team that won all four group games needs to be taken seriously.
"Topping the pool is fantastic and has got us into a quarter-final, but we want to go a lot further."
Ireland ran in three super tries at Otago Stadium with Keith Earls, who was celebrating his 24th birthday, crossing twice and Brian O'Driscoll running a tremendous support line for the third.
"Tries win games and for weeks we've been talking about not taking our opportunities. We have to be more accurate in those channels," said Kearney.
"When you get chances at a World Cup you must take them and we've starting to do that a little more. It's good to see us scoring tries."
Kearney insists the euphoria at demolishing Italy was quickly replaced by thoughts of Saturday's quarter-final against Wales.
"The excitement's gone already and that's how focused everyone is. There was more excitement and elation after the Australia game," he said.
"The fact it's a six-day turnaround makes a massive difference in terms of recovery. Wales will be on us before we know it."
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