Joe Schmidt says he has no regrets about leaving Johnny Sexton out of his plans for Ireland's shock defeat to Japan.

The 2018 World Player of the Year was deemed fit by the head coach during the week, but understudies Jack Carty and Joey Carbery were preferred in the match-day 23.

The Leinster out-half played 58 minutes against Scotland last week but declined goal-kicking duties after the second try and also received on-field treatment for a leg issue.

"I don’t think you ever regret utilising your squad because we were here four years ago and we kind of didn’t use the squad," Schmidt told RTÉ Sport after the 19-12 loss.

"We didn’t want to make that same mistake again because there is no guarantee that anyone is going to be fit at the end of the day, so guys have to get that opportunity."

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Carty, who made his international debut in this season's Six Nations, set up both of Ireland's first-half tries and converted the second, but failed - like the rest of the team - to make an impression in the second period. 

Schmidt added: "Jack had done very well against Wales away in the lead-up, he’s a guy who has impressed us.

"I thought he controlled the first half pretty well but once we came under pressure on the back of some penalties, they got that field position.

"It was very, very hard to get the ball off them, a lot of very deep cleaning in the ruck.

"We were getting taken out at least two or three metres past the ruck and that gave them the impetus to keep coming at us."