"I don't know if Wales feel like they are invincible. They're saying they have forgotten how to lose and all that," Sexton told reporters.
"We've played well against teams that have been on runs before when you talk about England, New Zealand and stopping their runs.
"We'll give them the respect they absolutely deserve. We'll analyse them, we'll talk about where we can get at them, where they are very strong. They look pretty tough to break down."
Ireland, who won the Grand Slam last year, have been far from their best in this year's championship.
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They lost to England in the first round and then produced unconvincing wins over Scotland and Italy, which Sexton blames on minor errors piling up.
"Honestly, there was nothing majorly broken in the first few games. There was just some uncharacteristic errors from some individuals and some break downs in just a couple of things," Sexton added.
"That just adds up and if everyone makes a couple of mistakes then suddenly you have 30 errors and you are in a bit of trouble."
(Reporting by Rohith Nair in Bengaluru; Editing by Christian Radnedge)
