"His passing is world-class and he has the capacity to get us out of jail. He's done that a couple of times in big games when there's been massive line breaks and you can see nothing but a try coming, and he comes out of nowhere to make a hand-trip or something.
"The best way to describe Peter is it's not the dog in the fight, it's the fight in the dog. He does box well above his weight, he puts in a huge number of tackles and he always tackles someone bigger than him, and he's a good organiser. He barks at the pack, he keeps them in line and they're all afraid to cross him. That dynamic is very important in a pivotal position," added the Ireland coach.
"Isaac (boss) did a very good job the last day, a slightly different player, and I thought he had a fine game, but I suppose Peter has that extra edge of experience, he knows the pack that little bit better so all those factors come into the equation. There's a little bit of pressure on Peter to come out with a big game, but he's one guy you don't worry about under pressure and the bigger the occasion the harder he works, and that's why it's good to have him back," said O'Sullivan.
And while the Gods seem to be smiling on Ireland this week the same cannot be said for England who have had to withdraw Jason Robinson while there is a doubt over Johnny Wilkinson.
Robinson sustained a neck injury in training on Wednesday and he will be replaced by Harlequins wing David Strettle who will be making his international debut. Robinson is a big loss to this England side because he has been in good form at international level but what would be catastrophic would be if England had to take the field without Wilkinson. Whether they like it or not, whether they want to believe it or not, England's outside chance of beating Ireland rests on the performance of Wilkinson.
Mick Catt has been drafted into the England squad as cover for Wilkinson.
Meanwhile, Eddie O'Sullivan has appealed for calm in an attempt to defuse mounting tension ahead of England's Croke Park debut on Saturday and he has chided the media for, "gleefully fanning the flames" ahead of the historic encounter.
"It's understandable that people will have issues in principle with what will happen on Saturday and they have a right to have those issues," It's understandable they want to express them. That's fine and healthy. It's free speech.
"But if I was to have a dig at anyone, it's at the media for gleefully fanning the flames - and not just the rugby media." said the Irish coach.