AUGUSTA, Ga. -- It was a practice swing unlike any other.

Zach Johnson, the 2007 Masters champion, stepped to the tee box on the 13th hole at the tail end of Amen Corner during Friday's second round.

Johnson teed up his ball, squared up his stance and took a practice swing. What came next might be a staple of every weekend hacker's repertoire but is something rarely seen on the PGA Tour, especially at fabled Augusta National Golf Club.

Johnson inadvertently hit the ball on his practice swing, sending it caroming off the tee marker on the right. The ball ended up about 3 or 4 yards in front of Johnson, who scooped it up and re-teed.

"Shoot, they got that?" Johnson said after the round when told video of the swing existed. "Yeah, that was a good one there. That's a first. I thought I'd done it all, but now I know I've done it all."

Under United States Golf Association rules, a ball isn't considered to be "in play" until it's actually hit from the tee area. Because Johnson didn't have the intention of hitting the ball, he was allowed to re-tee and hit again.

"Zach's eyes were as big as I've ever seen them. His jaw dropped and we had a good chuckle knowing that wasn't a penalty, but a not-so-top-10 moment." Matt Kuchar on Zach Johnson

The exact scenario is actually covered under Rule 18-2 in the USGA rulebook, "Ball at Rest Moved." If the mishap had happened on his second shot from the middle of the fairway, after he'd already hit his tee shot, he would have had to replace his ball in its original position and incur a one-stroke penalty.

The good news for Johnson: He hit his actual drive 285 yards down the middle of the fairway, knocked his second shot to 30 feet and two-putted for birdie on the 510-yard, par-5 hole.

"I can't think of a time I've done it -- not on purpose," Johnson said of hitting the ball during a practice swing. "Maybe I've tried to do it, but I don't think I could do it again even if I tried."

Johnson, whose round of 73 left him 3 over for the tournament, said he knew there wasn't a penalty involved because "it all comes down to intent."

"That's something we're going to laugh about for a long time," said Matt Kuchar, who was playing with Johnson and Ian Poulter. "I know there's supposedly footage of every shot hit here at Augusta this year, and I'm hoping to see that footage at some point.

"I didn't see it, but I heard it. Zach's eyes were as big as I've ever seen them. His jaw dropped and we had a good chuckle knowing that wasn't a penalty, but a not-so-top-10 moment."

Kevin Kisner, who was playing in the group in front of Johnson, said he'd never done it in a competitive round.

"Only if I've been drinking," Kisner said.