Muggy, overcast and breezy conditions greeted the early starters at the U.S. Open on Sunday as Tiger Woods again battled and overnight leader Phil Mickelson prepared for a late teeoff in the final round.
While Merion's East Course has given the game's best players a challenging test all week, it has also rewarded good golf shots and Canada's Mike Weir was among those to benefit, ending his tournament with a one-under-par 69.
Also faring well among the early starters were Scotland's Martin Laird, two under after 16 holes, and Japan's Hideki Matsuyama, two under after 10.
Three-times champion Woods, however, was heading for one of his worst ever finishes to the year's second major after covering his first 10 holes in three over.
Tournament favourite at the start of the week after winning four times in just eight starts on the 2013 PGA Tour, Woods birdied the par-four first but then ran up a triple-bogey eight at the second after hitting his tee shot out-of-bounds.
He also bogeyed the sixth and seventh as he continued to struggle with his putting on Merion's subtle sloping greens before registering a birdie at the driveable, par-four 10th.
At the business end of the tournament, several mouth-watering storylines were bubbling, among them whether Mickelson could finally celebrate his first U.S. Open win on his 43rd birthday and on Father's Day with his dad watching him play.
A four-times major champion, Mickelson has been a runner-up a record five times at his national championship.
"It's got the makings to be something special, but I still have to go out and perform and play some of my best golf," Mickelson told reporters after carding a level-par 70 in the third round for a one-under-par 209.
Fellow American Steve Stricker, joint second at even with compatriot Hunter Mahan and South African Charl Schwartzel, is bidding for his first major title. At 46, Stricker is also aiming to become the oldest U.S. Open champion.
"A win would be unbelievable," said Stricker, who returned a 70 in the third round. "But I'm out not trying to think about that yet. I'm just trying to execute the shots that I know how to do and take one shot at a time and go from there."
Luke Donald and Justin Rose, tied for fifth at one over overnight, are both aiming to become England's first U.S. Open winner since Tony Jacklin at Hazeltine National in 1970.
U.S. Open qualifier Shawn Stefani ended his week on a rousing note with a 69 after recording a startling ace with a four-iron at the 213-yard par-three 17th where his ball benefited from a fluke bounce out of the rough.
The American watched in amazement as his tee shot landed on mounding to the left of the green, then tracked some 60 feet from left-to-right before dropping into the cup just as it was running out of steam.
Stefani jumped up and down in delight before being embraced by his caddie and sharing high-fives with his playing partner Kyle Stanley.
"I was just super-excited because it's the first hole in one I've ever had in a tournament," said Stefani, who kissed the left rough in thanks after retrieving his ball from the hole.
"I was really surprised to see the ball kick to the right. Once it did kick, it kept rolling and I was like, 'Well this could be good'. And the fans stood up and then it kept getting closer and closer and then it went in."