Phil Mickelson, looking to become the oldest player to win a major, entered the final round of the PGA Championship with a one-shot lead over Brooks Koepka. By the turn, Mickelson's lead was two.
Here's how a frenetic front nine played out on the Ocean Course:
On the first hole, the 50-year-old Mickelson three-putted the first green while Koepka made birdie. Koepka led by one at 7 under.
Then after a two-shot swing in Koepka's favor at the first, there was a three-shot swing in Mickelson's favor at the second.
After Mickelson quickly lost his anticipated lead, there was a three-shot swing in Mickelson's favor at the second. Mickelson went on to make birdie, while Koepka made double bogey on the par-5 second. Mickelson led by two at that point.
On the par-4 third, Koepka missed a 3-foot putt for birdie, while Mickelson bogeyed, decreasing his lead to one stroke.
On the fourth hole, Mickelson and Koepka both made par.
After Mickelson hit his tee ball it into the bunker on five, he then holed it for birdie for the highlight of the afternoon, taking a two-stroke lead over Koepka and Kevin Streelman.
On the par-4 sixth, Koepka re-tied the lead with a birdie, where Mickelson bogeyed.
Then a two-shot swing at the par-5 seventh, Mickelson made birdie and Koepka made bogey to put Mickelson up two on Koepka and Louis Oosthuizen.
For the second time of the day, Mickelson and Koepka made matching pars on No. 8, placing Mickelson at 7 under and Koepka at 5 under.
To cap off the front nine, Lefty parred the par-4 ninth to keep a two-shot lead on Koepka.
And then they turned and headed toward the back nine.