By Andrew Both

KIAWAH ISLAND, S.C. (Reuters) -Phil Mickelson had to replace a damaged one-iron barely 20 minutes before the PGA Championship final round on Sunday but the setback did nothing to unsettle the 50-year-old American, who went on to become the oldest major champion.

Mickelson's caddie, his brother Tim, took off to retrieve a different club from his locker at Kiawah Island leaving Mickelson, the only player left on the practice range, to continue his warm-up with instructor Andrew Getson.

Mickelson later explained the face of his club had cracked on the range.

"You can't swing it as hard as I hit it and not expect

them to crack," Mickelson joked.

"Fortunately I had a four-wood that's a very comparable club to that one-iron distance-wise and I was able to use that club effectively. There was a few times that I hit it and I hit that club very well.

"It's just one of those things that happens and you just have to be prepared for it, which is why I bring backup clubs out here."

(Reporting by Andrew Both; Editing by Ken Ferris/Peter Rutherford)