Rob Kearney reckons whoever wins the Six Nations match between Ireland and England in Dublin on Sunday will still struggle to complete a Grand Slam.
Both teams head to Lansdowne Road on the back of first round victories, Ireland seeing off defending Grand Slam champions Wales 30-22 and England backing up their dramatic December triumph over world champions New Zealand with a 38-18 Calcutta Cup success against Scotland at Twickenham.
With pre-tournament favourites France having suffered a surprise loss to Italy, Sunday's match is already being billed as a potential Championship and even Grand Slam decider.
But Ireland full-back Kearney, ever-present in the 2009 Grand Slam-winning side, was not so sure.
"The sides in the Six Nations are now all so good, the days of Grand Slams are probably going to be minimised a huge amount," Kearney told a Lansdowne Road news conference on Saturday.
"For one team to win all five games is going to become a more and more difficult feat given the nature of how good all the other teams are," the 26-year-old, set to win his 43rd Ireland cap on Sunday, added.
"I think a lot of people had France down as potential champions but one defeat is not going to change that for them. There's going to be a lot of shake-ups every weekend in this competition and that's what makes it so good."
And the British and Irish Lion was in no doubt of the threat posed by an England side who beat the All Blacks by a commanding 17 points.
"I've been really impressed with them. That big win was huge for them, that they won significantly well against easily the best team in the world.
"That's no mean feat whatsoever. They've gotten a lot of plaudits for it, and rightly so, they deserve it.
"And then you always watch closely if teams can back up big performances like that and they have done against Scotland. We are under no illusions as to what we are up against. There's a quality side coming to Dublin tomorrow (Sunday)."
Ireland stormed into a 27-point lead early in the second half at the Millennium Stadium only for a ferocious Wales fightback to cut their eventual margin of victory to single figures.
"Your first game up in the Six Nations, it's always really important to get off to a good start," said Kearney.
"The first 40 minutes we did that...I think it was pretty obvious the contrast in the two 40 minutes and a lot of that is down to things we can control. We learnt a big lesson from that second half."
England have opted against recalling Manu Tuilagi to their starting side after the powerful centre, one of the stars of the win over New Zealand, missed the Scotland match with an ankle injury.
Instead they've stuck with Billy Twelvetrees, who made a try-scoring Test debut last week, and Brad Barritt, with Tuilagi on the bench.
Ireland defence coach Les Kiss, said there was no great surprise in England's centre pairing or mystery in the approach needed to counter Tuilagi .
"You can see the rationale of why they didn't put Manu on to start the game," said the former Australia rugby league wing.
"He hasn't played a lot of rugby recently and you can see a plan that they want to unleash him on us later on," Kiss added.
"When he comes on, we've just got to make our tackles, haven't we?"