UPDATE 1-Golf-Johnson left red faced after practice swing gaffe

American Zach Johnson accidentally struck his ball during a practice swing on the 13th tee in the second round of the Masters on Friday, producing the kind of cringe-worthy moment every golfer dreads. Johnson, giving his club a forceful swing through the air, clunked the ball into the marker, proving that even major champions can make silly mistakes.

"That's a first. I thought I had done it all but now I know I've done it all," Johnson said after his round. Luckily, the 43-year-old emerged unscathed -- pride not withstanding -- as no penalty was applied and he went on to birdie the 13th hole.

"I was caught off guard," Johnson said. "I actually hit a really good tee shot after that, so I think I recovered nicely." Johnson ended his second round with a 73, a slight improvement over his day-one score of 74, as he aims for a repeat of his Masters-winning performance 12 years ago.

As for repeating his 13th-hole gaffe today? "I don't think I could do it again if I even tried," Johnson said. (Reporting By Amy Tennery, editing by Pritha Sarkar and Toby Davis)