Joe Schmidt reaffirmed that Saturday's heavy defeat to England was an "unacceptable result".
The head coach made a rare appearance at a Tuesday press briefing in Co Kildare.
He said: "It's an unacceptable result for us, a performance beneath where we need to be. The whole group are very conscious that we have a short period of time that we accelerate what is part of a progression.
"We had a vigorous pre-season, we tried to taper but we looked, flat, slow inaccurate and we didn't adjust when we see we were getting troubled.
"Nothing mitigates losing the way we did. We've tried to periodise our lead-in to the World Cup. At this time of season you get some bizarre results."
"Hopefully you'll see evidence of [improvement] this Saturday [against Wales] and if you don't and we don't then we are going to be under real pressure."
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Schmidt confirmed that "Conor [Murray] trained fully and did all that was required" and has passed all Head Injury Assessment protocols after taking a heavy hit against England.
Johnny Sexton is unlikely to be risked for Saturday's game in Cardiff, he said.
"Johnny got put back with thumb injury and was trying to catch up a bit and got stiff and sore. He again is very keen to be involved.. if he had to play this weekend he could," said the coach, while denying the out-half had a leg injury, as reported over the weekend.
Cian Healy won't feature this weekend after being forced off at Twickenham at the end of the first half.
"Cian is bullish, probably play the week after [Wales at home]," he said.
The news about wing Keith Earls was less promising.
"[It's] really frustrating for him. He looked super sharp, he got a little bit of tendenitis just above the knee, it's just niggling away.
"It's about playing the long game with Keith and making sure that he's ready to go. I know that he'll be ready for the weekend after this one but I doubt he'll be involved this weekend."