– Star golfers let loose on Twitter on Sunday after the USGA informed Dustin Johnson that he might face a retroactive penalty after his ball moved on the fifth green during the final round of the U.S. Open.

Jordan Spieth tweeted: "Lemme get this straight. DJ doesn't address it. It's ruled that he didn't cause it to move. Now you tell him he may have? Now? This a joke?"

Johnson played the final two hours without knowing where he stood when the USGA questioned whether he should be penalized one stroke. He said he did not cause the ball to move, and he was backed up by playing partner Lee Westwood.

Rory McIlroy tweeted: "This is ridiculous. No penalty whatsoever for DJ. … Amateur hour from @USGA."

Rickie Fowler wrote that he stood with Spieth and McIlroy, adding: "The fact that the @usga thinks that DJ caused the ball to move is completely ridiculous! Laughable!"

After the round — when it was apparent Johnson would be champion — the USGA assessed the penalty. Johnson''s round of 69 was good enough to win by three strokes over Jim Furyk, Scott Piercy and Shane Lowry.

For perspective, if this tournament were conducted by PGA Tour norms, Johnson's simple statement to an official at the fifth hole that "I didn't make the ball move" would have been sufficient to settle the issue.

Pro golfers play by a code of honor that 99.99 percent take utterly seriously. Johnson has called penalties against himself in the past in circumstances where no one else could see what happened.

But this is the USGA.

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