Willett reached a career high of ninth in the world after claiming his first major title at Augusta National in 2016, but had slumped outside the top 450 earlier this season after suffering numerous injuries and a loss of form.
A missed cut in the French Open was his ninth in 12 events, but the 30-year-old, from Sheffield, bounced back to finish sixth in the Irish Open and 19th in last week’s Scottish Open at Gullane.
This upward trend continued with an opening 69 in the Open Championship at Carnoustie, which threatened to be even better when the former Ryder Cup player reached four under par with five holes to play.
“That was good and we had a lot of 12, 15 footers as well that just slid by,” said Willett, who dropped shots on the 17th and 18th.
“Could have been a really, really nice knock, but at the end of the day it wasn’t.
“It’s definitely nice to be stood here after shooting a relatively stress-free 69. You look at the number as a whole and not how we finish or how we start.
“It’s a number in the 60s and we’ve had a few the past couple of months, which has been really nice.
“As much as you don’t like getting up at 4.20am, you can go back and get your feet up. You know there’s going to be some good scores and you’re going to tumble down the leaderboard, but you’ve done your shift and you can go get ready [for round two].
“I’m pretty hopeful we’ll never be in as dark a place as we were. It was pitch black.
“But this is a strange, odd game. You get ebbs and flows and hit a low point, but I’ve really enjoyed golf the last six, seven weeks.
“Even getting the clubs out and going to play at home without having to do two hours of warm-up and go see the physio felt pretty good.
“That kind of leads you to work a little bit harder, even if it’s just an extra half an hour putting and an extra half an hour hitting balls.
“And the little sessions you’re able to do for a bit longer because your body is better and just enables you to gain a little more than you ordinarily would have. Then to be able to go home and not have to go through treatment, it’s nice.
“Regardless of what the golf is and how the golf is, it’s a lot better place to be.”
Matt Fitzpatrick, Willett’s fellow Sheffielder and 2016 Ryder Cup team-mate, began with a one-over-par 72.
After a solid start of five successive pars he birdied the par-5 sixth.
However, he gave the shot back at the eighth to be out in level par and returned to the clubhouse in one over, his only other birdie of the day, at 14, being sandwiched by bogeys at 13 and 15.
Henrik Stenson was satisfied with his first round after overcoming injury to compete at Carnoustie. The 2016 champion’s preparations for the tournament were hampered by an elbow problem that forced him to miss last week’s Scottish Open.
The Swede carded a one-under-par 70 yesterday.
The 42-year-old said: “I’m happy with the score. I’m happy with a fighting performance.
“I feel like I’m behind on practice and playing and preparation. We’re just trying to do the best with what we have and what we can do, and we’ll see where it takes us.
“The elbow is okay. It’s not 100 per cent, but it’s good enough to play, obviously, otherwise, we wouldn’t be here this week.”
Howley Hall’s Marcus Armitage, who was carrying a shoulder injury going into the Open, suffered a disappointing day in his first major after qualifying at St Annes Old Links.
Bogeys at one and nine bookended a two-over-par run to the turn.
However, after parring the 10th he dropped seven shots in the next seven holes with five bogeys and a double at 16.
Pannal’s Tom Curtis, who qualified at The Renaissance Club at North Berwick earlier this month, endured an even more torrid major baptism.
Through six holes he was just one over par having birdied the par-5 sixth after bogeys at two and four.
However, he began a nightmare run at the ninth with a bogey that was quickly followed by a double bogey at 10 and another dropped shot at 11.
A par at 12 brought temporary relief, but was followed by a fifth bogey of the round at 13 and a sixth at 16.
The 33-year-old then sank to the bottom of the field – albeit in exalted company alongside 2011 Open champion and former Ryder Cup captain Darren Clarke – with double bogeys at the finishing two holes leading to an 82.