Sergio Parisse has admitted Ireland caught Italy on the hop by handing Ian Keatley his RBS 6 Nations debut this weekend.

Italy captain Parisse conceded the Azzurri fully expected Joe Schmidt to start Ian Madigan at fly-half for tomorrow's Stadio Olimpico clash (2.30pm) in Johnny Sexton's absence through concussion.

Parisse claimed Italy will not single out Munster's Keatley to try to prey on his inexperience, but admitted the three-cap out-half will be under intense pressure.

The richly-talented Stade Francais number eight has challenged Italy to justify their Six Nations place all over again following a winless 2014 in the competition.

"We didn't expect probably to play against Keatley at number 10: we thought in our minds that it would be Madigan," said Parisse.

"In any case, they are two different kinds of player. Madigan is the kind of play that attacks the line more, a good step and Keatley has another kind of game.

"From the tactical point of view, he's probably more similar to Sexton.

"From our point of view, we don't really focus our strategy on Madigan or Keatley, we just study Ireland as every team does in the Six Nations and try to put them under pressure.

"I suppose for him it's a great opportunity.

"He will have great pressure on his shoulders before the match tomorrow, but he plays for Munster and has the attitude to play at good levels.

"We don't think too much about that: we must keep pressure on him, but not just only on him.

"Obviously with any team you want to put the number 10 under pressure.

"When you have an opportunity to play for your country in a match in the Six Nations, there is a big responsibility, big pressure. So it's for him to manage this pressure.

"For my point of view, the Italian point of view, we want to put pressure on him and all his team, but we don't focus just on him and focus just on his match."

Parisse admitted Italy must produce one of their best-ever performances to have any chance of toppling the reigning champions this weekend.

"We just study Ireland as every team does in the Six Nations and try to put them under pressure"

The Argentina-born 31-year-old also warned Ireland that if they slip off the pace, the hosts will be ready to pounce.

Parisse has been at the forefront of northern hemisphere rugby for the last decade, but conceded it is time for Italy to start progressing.

Italy's 108-cap talisman said coach Jacques Brunel's side cannot rely on heart and pluck alone against Ireland this weekend.

"I really feel that if Ireland play at 60 or 70% against us they are not going to win tomorrow: they must play at 100% to beat us," said Parisse.

"So it's going to be tough for Ireland. But for us, if we don't play at 110 or even 150%, then we don't have any chance of winning.

"I'm really confident in our team and our plan though, and that we'll put everything into getting the win.

"We know it's not enough to play with passion and energy against Ireland. We have to show that we can play quality rugby as well.

"Tomorrow's going to be crucial for us to show to the Irish team that Italy is not just passion, that Italy is not just energy, it's quality rugby as well. This is the big chance for us.

"And as I said before we'll play against a really quality team tomorrow and I'm really confident my team is ready to play a great match this weekend.

"I'm really confident Italy has the ability to compete seriously in the Six Nations.

"But every year we must show we really deserve to play in it, otherwise we will struggle and we know the tournament is tough for everyone.

"It's a new year, so we have the chance to prove we deserve to be here all over again, and that's what we want to do."

Live coverage of Ireland v Italy (Saturday 1430 at Stadio Olimpico) from 1330 on RTÉ2 and RTÉ Player.