The minor setback did little to disrupt the 50-year-old's preparation as he became the oldest Major winner ever.
Mickelson Cracked His 2-Iron Minutes Before PGA Championship Final Round
The oldest Major champion ever suggested that the club worked effectively, even though he only achieved a bogey and par on those holes.
"As I was teeing off today my 2-iron face cracked," Mickelson said during his post-tournament interview.
He then joked about how his power caused the club to crack.
"I mean, you can't swing it as hard as I hit it and not expect them to crack - I'm kidding."
However, there is an element of truth in Mickelson's comments about his power.
He hit the longest shot on the 16th hole all week, driving the ball an incredible 366 yards.
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Mickelson described how Tim first noticed the cracked club after he handed it back to him.
"Tim noticed when I put it back that it had cracked across the face," he said.
"Fortunately I had a 4-wood that's a very comparable club to that 1-iron distance-wise and I was able to use that club effectively.
"I used it off 3 tee, 4 tee, and 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."
All players will use a full 14-club set, though the six-time Major winner is known for travelling with up to 25 clubs in case of changing weather conditions or emergencies.