NORTON — Cognizant of his own name sitting atop the list, Paul Casey glanced at the Deutsche Bank Championship leaderboard after birdieing the 16th hole Sunday at TPC Boston. What he didn’t realize was how tight the pack was behind him, his one-stroke lead barely an advantage.

Casey made par on No. 17 to remain at 3 under for the day with one last chance to pull away before Monday’s final round.

“So frustrating to leave the putt on No. 17 shy of the hole,’’ Casey said. “Although I hit a wonderful shot in there, landed exactly where I wanted it to, it just didn’t release.

“But at no point, having looked at the leaderboard, did it transfer into then thinking about or making my decision different at No. 18.’’

The 39-year-old Brit acknowledged he pushed his tee shot on the par-5, 530-yard 18th hole, but the drive put him 235 yards from the pin — “wonderful yardage,’’ he said — and he was left to contend with only the wind.

“The wind was coming in at sort of a 10 o’clock angle,’’ Casey said. “And I was just about to hit it and the wind had picked up and my thinking was, ‘Well, it’s picked up here but it’s going to probably mean that it’s calmer by the green.’ ’’

John McLaren, Casey’s caddie, held him up.

“Johnny actually said to me, ‘Stop, stop, just don’t,’ ’’ Casey said. “I obviously had been sort of waggling the club and dancing the feet around. I’m glad he stopped.’’

Casey’s delayed shot sailed into the wind at just the right moment, headed left, then carried back to the right. There was a roar from the crowd by the 18th green as the ball landed, then a collective groan as the fans watched the shot stop rolling just feet from the hole.

Casey sank the putt for eagle, putting a stamp on his third straight day at 5-under 66 to take a three-stroke lead at 15 under. Brian Harman sits in second after three days of competition at 12 under. Smylie Kaufman, Jimmy Walker, and Kevin Chappell are tied for third at 11 under.

“I feel great with the way I played today,’’ Casey said. “I saw some scores that guys like Louis [Oosthuizen] had posted early in the day, although early in the day was, I felt, just as difficult as what I faced this afternoon.’’

Casey said he was amazed by Oosthuizen’s score, a 7-under 64 that catapulted the South African into a tie for seventh.

“And to be sitting here with a 66,’’ Casey said, “I’m obviously over the moon.’’

The former Arizona State University golfer made par on Nos. 1 and 2 to begin the day, then bogeyed the par-3, 208-yard third hole. He made par on No. 4 before stringing together three straight birdies on Nos. 5-7.

“Ball-striking was great once again,’’ Casey said. “It’s really been sort of the foundation of what’s already been a great week. Even with the great ball-striking, I found it difficult at the beginning, but to turn it around and have a lot of looks for birdies and make a few to come in with, it’s been great.’’

On the back nine, Casey made par on Nos. 10-15 before using the final three holes to set himself apart from the rest of the players still in the hunt.

The extra separation may be key on Monday for Casey, who will not only have to hold off the golfers behind him as he tries to secure his second PGA Tour victory, but could be playing in severe weather conditions caused by the remnants of Hurricane Hermine.

Regardless, he’ll be looking at the leaderboard once again, though he insists the glances won’t change his game plan.

“I’m pretty confident that John and I have got a good way of playing this golf course,’’ Casey said. “[Our strategy] might be stressed tomorrow with the conditions, we’ve got to stick to that. We’ll only change it I think if we need to, maybe on the last couple of holes if we need to push.

“You can see what can happen. There’s an eagle to be had on No. 18, there’s birdies to be had on No. 17, but we’ll see.’’