Zach Johnson took down the hottest player on the PGA Tour in Sundays final round of the Crowne Plaza Invitational at Colonial, helping caddie Damon Green honor his late father in the process.But Johnson got busy celebrating a memorable moment on the 18th green and incurred a two-stroke penalty that would have been costly if not for one mitigating fact: He led playing partner Jason Dufner by three strokes at the time.The large cushion turned Johnsons two-stroke penalty at the 72nd hole into an oops moment he could dismiss as a brain cramp at the conclusion of a one-stroke triumph rather than a title-changing mistake that would live in infamy.Appropriately, Green in concert with PGA Tour rules official John Munch let Johnson know about a mistake hed made in regard to marking his ball at No. 18 before he signed his scorecard. Under the rules of golf, signing an incorrect card would have resulted in disqualification.I got lucky they told me before I signed, said Johnson, who posted a double bogey, rather than a par, on his closing hole to finish 12 under par for the tournament and secure his second Colonial plaid jacket in the past three years. Im glad no one took a gun at the end and shot me because of my stupidity ... There are a number of adjectives that I am calling myself right now, and lucky would be the biggest one. Blessed would be another. Its an honor to put this jacket on once. Im in shock I got it twice.Johnson, who won his first Colonial title in 2010, did everything necessary between the ropes to separate from Dufner, last weeks winner at the HP Byron Nelson Championship, in a back-and-forth final round that saw both players deadlocked, at 14 -under, on the 14th tee.Johnson made a 9-foot birdie putt at No. 14, seizing the final lead change in their Sunday duel, then benefited from Dufners errant approach at No. 15. It wound up in a water hazard behind the green, leading to a triple bogey that gave Johnson a four-stroke margin to protect over the final three holes.Because of a bogey at No. 16 and the procedural snafu at the 18th green, Johnson needed every bit of that margin to avoid a playoff with Dufner, the 54-hole leader who was trying to become the first golfer to win both D-FW tour stops in consecutive weeks. Dufner, who found only 3 of 14 fairways during a final-round 74, blamed himself for not being in position to take advantage of Johnsons gaffe on the final green.Its not bad luck. Its just bad play, Dufner said. I couldnt get a ball in the fairway all day. For 17 holes, Johnson balanced three birdies, three bogeys and 11 pars in swirling, 25 mph wind gusts. But after moving his ball mark at the 18th green to avoid being in Dufners putting line toward the hole, Johnson forgot to move the mark back to its original position before holing his final putt. Thats a two-stroke penalty, causing Johnson to post a 72, his first over-par Colonial round since 2006.Ive never done that before, said Johnson, who plans to avoid a repeat for the duration of a PGA Tour career that now includes eight career titles, including one at the 2007 Masters.Among his victories, Johnson said Sundays triumph at Colonial stands out for two reasons. From a golf standpoint, he defeated Dufner who sought his third victory in the past month in a head-to-head setting.I feel like I unseated a king, because hes been on top for the last four weeks, Johnson said. Even better, said Johnson, is that he helped Green his caddie for nine-plus seasons honor his late father, who died May 17 of stomach cancer. Colonial marked the first tournament appearance for the Johnson-Green duo since the death of the Rev. Douglas Brooks Green, 88. After making his final putt, both Johnson and Green pointed toward the sky in honor of Rev. Green.I think Damons the one who should be rewarded, said Johnson, who earned $1,152,000 with the victory. Hes the guy that probably put more sweat into this than I did. It was so courageous ... after his father passed, to come here and be focused and carry me. He felt like his dad wanted him to be here. Thats commendable, and I feel lucky to have him.Even luckier, in retrospect, that Green was the one who alerted him to his procedural error at No. 18 before Johnson could sign an incorrect scorecard.