Koepka's been on staff with Nike and Srixon, as well as having a successful stint as an equipment free agent. And yet, even through all the changes, two clubs have managed to fend off the competition: Nike's Vapor Fly Pro 3-iron and TaylorMade's M2 3-wood.

While the former remained in the bag at the Alfred Dunhill Links Championship, Koepka made a surprise move and replaced the M2 3-wood with a TaylorMade R7 Quad mini driver.

Whether this is a one-week tweak for links golf or the start of a longer move away from the M2 remains to be seen. Koepka, who's three shots back of the lead heading into the weekend, hasn't spoken about the club change. But based on photos I captured during the PGA Championship, the 3-wood was showing serious signs of wear.

In other words, it may have simply been time to replace it. As for the mini driver, the club has become a bag staple for several high-profile names in recent years, including Tommy Fleetwood, Adam Scott and Rickie Fowler, because it offers versatility off the tee and from the turf.