Neither player realized the error until they reached the green. The penalty for playing the wrong ball is two shots, so the players had to return to the spot where they hit the incorrect golf balls and play from the correct spot.

We’ll give them the benefit of the doubt and chalk it up to competitive rust. At last week’s season-opening event on the PGA Tour, Will Zalatoris and Cam Davis found themselves guilty of a surprising—and expensive—rules blunder: playing the wrong ball.

A mix-up between Australian Cameron Davis and American Will Zalatoris in the final round of The Sentry on Sunday led to both golfers walking away from the tournament with significantly reduced prize cheques.