While Declan Kidney's side are out of the running for the title they have one of the meanest defences in the competition with only England conceding fewer points.
The Irish defence has also seen their tryline breached by only two sides - defending champions Wales on the opening weekend and Louis Picamoles' 74th-minute try for France last weekend.
And after making three changes to the side who pushed England all the way at Twickenham, Brunel is under no illusion as to the task Italy face on Saturday in Rome.
"After France we weren't able to play the same game against Scotland. Now we have played an interesting game against England, let's hope we can do it again," he said.
"The impression we will give on the overall tournament will come from the performances against Ireland, and the result. I remember the last time we played them, we conceded 40 points in Dublin.
"At half-time it was close but then in the first two minutes of the second half we conceded two tries.
"But we have to look at Ireland in this tournament, they have beaten the Welsh and haven't conceded tries against England, Scotland and only one at the death against France, from a quickly-taken penalty.
"They have a very well-structured defence, so it will be very difficult for us. They have very few weaknesses."