So many rules

PGA Championship 2023: Phil Mickelson cleverly uses rules to his advantage at Oak Hill

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Phil Mickelson has always been a man keyed into his equipment, and he seems especially so this week at the 2023 PGA Championship.

You may have heard of the "one-ball rule" before. This is a rule that pro tours often institute during competitions which, basically, stipulates you have to use the same make and model of golf ball during your round. You can switch out balls between holes, as long as it's the same type.

The one ball rule is an optional condition that Committees may choose to use. If this rule is in effect, you must play with the same brand, make and model of golf ball that you started the round with. This means that if you start playing with a Titleist Pro V1, you must play a Titleist Pro V1 for the remainder of the round and may not switch to another brand or even another model of Titleist golf ball.

The key word there is "optional." This, like the proposed golf ball rollback, is technically a "model local rule (MLR G-4)," which means it's not a standard part of golf's everyday rulebook. It's an add-on, like adding guacamole to your Chipotle order. Tournaments can decide to enact the optional rule whenever they want. The PGA Tour uses this MLR on a regular basis, as does the USGA for its championships.

One eagle-eyed viewer at the PGA Championship this week noticed that Phil Mickelson was swapping out golf balls during his first round at Oak Hill.

You could spot it on the broadcast. Notice the markings on the ball; here's Phil using a golf ball with the official "triple track" alignment markings.

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And here he is with no triple track markings, and instead a variation drawn on with two shorter lines and one longer one.

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It's unclear how different the golf balls are before that—whether one is softer for shorter holes and the other is longer for longer ones, for instance—but Mickelson noted after his round there is no one-ball rule enacted for the PGA this year (something the PGA of America confirmed to Golf Digest) and thus no potential breach of Rule G-4.

At the time of writing Mickelson is currently +4 through 25 holes of the tournament, and in T-67.

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