As expected, his playing partner's speed irritated Koepka on Sunday.
"When it's your turn to hit (and) your glove is not on, then you start thinking about it," Koepka said, according to Golf Channel's Will Gray. "That's where the problem lies. It's not that he takes that long. He doesn't do anything until it's his turn."
Koepka, who said Holmes isn't the only one on the PGA Tour often not prepared to hit, appeared frustrated during the round. He's seen below walking away from the green as Holmes lines up his putt using the plumb-bob technique that's been scrutinized in the past.
Additionally, Koepka stared at an official while pointing at a non-existent watch after the 12th hole, indicating he wasn't pleased with Holmes' pace, according to Gray.
Even with Holmes' apparent slow play, the pairing kept pace for 13 holes, and Koepka takes full credit for that.
Koepka started the day 4-over through four holes, which certainly didn't help his demeanor. He finished the tournament at 6-under and in a tie for fourth.
Things didn't go nearly as well for Holmes, who turned in a 16-over 87 for the highest final-round score in an Open Championship since 1966. Holmes fell from third place to begin the day to a tie for 67th.