(Reuters) - U.S. Open champion Dustin Johnson birdied four of the final five holes to open up a three-shot lead over Paul Casey after the third round at the BMW Championship in Indiana on Saturday. Johnson delighted fans with another display of long hitting but also displayed a deft touch on slow greens at Crooked Stick in Carmel. He carded a 68 to post an 18-under-par 198 total, while Englishman Casey also shot 68 to lurk in second place at 15-under, with American J.B. Holmes (68) another shot back. ... More...