Coming off the first PGA Tour win of his career, Ken Duke had one of the more promising starts Saturday in the third round of the AT&T National at Congressional Country Club.

The journeyman who won last week’s Travelers Championship on the second hole of a playoff carded five birdies on Saturday’s front side and made the turn within two shots of then-leader Jordan Spieth. At that point, Duke said, his aim was to shoot 1 under or par the rest of the way.

But at 44 years old, Duke’s body was unable to hold up over the back nine, with the hilly and humid conditions conspiring to unravel his round as he finished five shots off the pace. He shot 1-under-par 70 and is 2 under for the tournament.

“The back nine’s tough. I just got tired,” Duke said. “I hit a few bad shots. I didn’t hit fairways. You’ve got to hit fairways here, and I had a pretty easy bunker on 17 but just flat-out looked up on it and skulled it. This golf course will beat you up. I played it pretty good for two and a half rounds, but the last part of the third round kind of got me.”

The misadventures from the sand at 17 yielded double bogey, and by the time he made par on the 18th, Duke had played 27 holes in one day. Duke was among the players who had to complete their second rounds Saturday morning after rain late Friday afternoon halted play.

Duke indicated his strategy heading into Sunday was simply to enjoy himself following a milestone victory in Cromwell, Conn. Duke was ranked 144th in the world before the win and was making his 187th start on tour.

“We’re taking this week as trying to have fun, kind of celebrating last week,” said Duke, who turned professional in 1994. “Sometimes when you do that, you hit some good shots, and you never know. You might play well.”

Mostly good for Gillis

Tom Gillis’s 5-under 66 was the second-lowest score Saturday, but included in that round was a shot that hit a female spectator on No. 18. Gillis initially was unaware he had hit someone until he made his way down the fairway, at which point the woman’s husband informed Gillis of what had happened.

The ball connected with such force that the spectator was somewhat teary, and Gillis immediately apologized. Gillis said the woman appeared to be in good spirits even though she had been hit.

“It’s painful,” Gillis said. “I’ve been hit in the head. I know what it feels like. I just tried to sign a glove for her. . . . I know it’s not going to take the pain away, but hopefully this glove is going to be worth something someday, so I’m really sorry.”

Gillis went on to bogey the hole. It was his second bogey of the round, which also featured seven birdies that left him two shots off the lead.. . .

Over the past few years, the PGA Tour has acquiesced to fans and allowed cellphones on the course at its events, provided they remain on silent or vibrate. There are, though, the occasional gaffes as Jason Krokak, who sits just one shot off the lead, found out at No. 8 right as he brought his putter back.

“The guy actually answered the phone and went behind a tree and started talking anyway,” Krokak said, “which I thought was pretty funny.”

Krokak actually made the putt for birdie. . . .

James Driscoll, the 35-year-old University of Virginia product who has earned more than $5.1 million on tour but never won, began working with Englishman Peter Crone on turning around his attitude in February.

“Not even really sports psychology,” Driscoll said. “It’s more of like a life coach. You just try to get everything in order and then hopefully the golf falls into place, and that’s kind of what I feel like has been happening over the last few months.”

Driscoll’s 68 Saturday gave him three straight rounds in the 60s — the first time he’s done that in his past 27 tournaments, dating from last June.

Missing the cut

Among the notable players who missed the cut at 3 over were K.J.Choi, Trevor Immelman and Justin Leonard.

Choi won the AT&T National during the tournament’s inaugural year in 2007 but this time came undone in the second round with a 5-over 76, leaving him one shot below the cut line.

Immelman, the Masters champion in 2008, was not able to recover following an opening-round 77.

Leonard, meantime, was one shot back of Immelman. The British Open champion in 1997 also won the Kemper Open that year at TPC Avenel, which is around the corner from Congressional.