The 2016 Masters champion had just three-putted the par-5 17th at The Belfry when he hit a shocker off the tee at the 18th into the water on the left of the fairway.
He limited the damage to a bogey following a brilliant fourth shot to open with a three-under 69 - three off the lead.
“Bad, just bad,” said Willett of his effort from the tee. “Just didn’t commit to anything, but at least hit a nice 9-iron and nice putt to salvage a bogey in the end.”
While the morning starters faced a testing wind, Willett and others in the afternoon wave enjoyed almost flat-calm conditions.
“I didn’t quite get the most out of the day, didn’t really hole any bonus putts,” added the Sheffield man, who is bidding to succeed where previous hosts Ian Poulter, Luke Donald, Lee Westwood and Justin Rose have all failed by landing the title.
“It was a real shame on 17 and, if you could go back 25 minutes, it would be nice. We’ve had a few long days and you feel a little bit tired.
“But we’ve not done anything silly today and we’re now in a nice position to hopefully have three solid days and keep moving ever closer to the top of the leaderboard.”
Pacesetter Matthias Schwab, meanwhile, insisted he had no complaints about missing out on a place in the year’s second major, next week’s US PGA Championship at Kiawah Island.
Schwab is set to miss out due to the vagaries of the qualifying criteria. The PGA of America usually invites all players ranked inside the world’s top 100, with more added if necessary to complete the field.
Twelve players outside the top 100 on 9 May were given invitations and 10 of those were ranked between 101 and 122, but world No 113 Schwab was overlooked.
“I have no idea where I am on the alternate list. They don’t really communicate anything,” said Schwab. “But I should have played better the last few weeks and that would have taken care of it.
“If I get in by Friday or Saturday I would love to play in it, but I wouldn’t travel as an alternate.”
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