How did the former World No.1 miss this?

WATCH: Justin Thomas Misses Tap-In Putt At The Open

Justin Thomas made a costly error on day three at The Open as he nonchalantly went to tap in a bogey putt on the 3rd hole.

JT’s par putt slipped by the hole and he then inexplicably missed the follow up, which was no longer than 18 inches, to card a double bogey.

Watch the putt below:

“Oh deary me,” Sky Sports commentator Richard Boxall said.

“Smack on the back of the hand for that. That’s embarrassing” Andrew Coltart said on commentary.

Related: What is Justin Thomas’ net worth?

JT slipped from one-under to one-over with the double bogey.

He opened with a 72 (+2) on Thursday and a superb 67 (-3) in round two got him to one-under for the tournament.

The former World No.1 plays in his fifth Open Championship this week.

His previous best finish came at Royal Portrush in 2019 where he was T11th.

Thomas won his first and only Major to date at the 2017 PGA Championship at Quail Hollow in Charlotte, North Carolina.