Wales boss Warren Gatland says he and his management team will discuss making a stance over his side's indiscipline following their 27-12 loss to Ireland.
Lee Byrne was sin-binned and Ireland scored two tries in his absence. Wales suffered a similar fate when Alun Wyn Jones was sin-binned against England.
Gatland said: "I suppose at some stage you've got to make a stance on a few things and for us again it was costly."
Wales could also make changes to face Italy on Saturday after defence lapses.
Full-back Byrne was sin-binned in the 25th minute of the Six Nations clash at Croke Park for knocking the ball out of scrum-half Tomas O'Leary's hands at a ruck.
Tries by Keith Earls and O'Leary followed while Byrne was off. Against England, Wales leaked 17 of the 30 England scored when lock Jones was in the bin for a trip on hooker Dylan Hartley.
Gatland said: "We need to speak to the coaches and discuss it with Lee.
"He's going to be pretty disappointed with himself, but I suppose at some stage you've got to make a stance on a few things and for us again it was costly.
"Again a yellow card has been costly for us and we need to look at that as well and just put our hands up and be honest about making sure that we cut those things out because it's been very costly for us.
Wales discipline frustrates Gatland
"It's hugely frustrating because the boys have been honest in team meetings and they've had a bit of a dressing down.
"So obviously when you see how costly it was at Twickenham and the same mistake is repeated and you get the same consequence, it is hugely frustrating for us."
The official match statistics stated Wales made 63 tackles and missed six for a completion ratio of 91% while Ireland made 121 tackles, and missed nine for a 93% return.
Gatland said: "They [Ireland] had some really strong runners. They made some line-breaks against us. We've missed a couple of first-up tackles which was disappointing.
"It's probably something we need to look at addressing. Whether we just get the balance right between we've got some great attacking players, but we've got to also make sure that defensively we're a little bit stronger as well.
"So that's something we need to go back and have a look at as well. We've got to look at that [changes]."
Gatland will also assess the what led Wales to have the majority of possession and territory and yet be unable to capitalise.
He said: "We've got to look at the positives in terms of territory and possession.
"The line-out struggled, particularly in the first half, then it came right then a couple of critical ones at the end which were costly.
"I thought in the scrummaging we had Ireland under pressure apart from one scrum, which was a key moment in the game. If we'd had got seven points.
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