The Sheffielder carded six birdies in a flawless round on Saturday which, at the time, equalled the course record.
Willett was three off the lead when he signed his card, but the wind had already dropped considerably and the final groups were cashing in, effectively taking away the chance of adding a Claret Jug to his 2016 green jacket from Augusta.
Shane Lowry took full advantage to shoot 63 and at the end of the day Willett was nine behind and his prospects of blasting his way to the top of the leaderboard were remote.
A final round of 74 yesterday saw the Yorkshireman finish in joint sixth, a shot behind Worksop’s Lee Westwood, and 10 shots behind Lowry.
Fellow Sheffield Matthew Fitzpatrick (after rounds of 71 69 70 73) was four shots adrift of Willett.
“You often get it where the guys go out early doors and have it flat-calm and the wind comes in when the tide changes and it is brutal out there,” Willett said.
“This is how it should be. If you play well over 36 holes you should get the best weather.”
Willett could console himself, however, with the fact he feels his game is back on track following a major slump because of a loss of form and injury after his Masters victory.
He won the DP World Tour Championship in Dubai in November to prove he was heading in the right direction and a new calmness about his situation has helped.
“It’s never not fun to shoot 65 on a Saturday at The Open. A lot of things are are going well,” he added.
“I’ve said it for the best part of 12 months now.
“The results aren’t what you want them to be, but the work I am putting in is good and it feels inevitable as to when you win again.
“It might be this week, it might be next week, it may be in a month’s time, but there is enough good in there to do it again, which is a nice feeling as it gives you that another bit of sunlight at the end of it.”