(Reuters) - Dustin Johnson said his score did not reflect the quality of his play, but it was good enough to lift him to a one-stroke lead over fellow American Kevin Chappell after the second round at the Tour Championship in Atlanta on Friday. Johnson and Chappell separated themselves from the pack, with third-placed Kevin Kisner and Japan's Hideki Matsuyama four strokes from the lead at three-under 137. "Three-under’s a great score around here, I’m never going to be upset with that but I felt I played really well today." The long-hitting world number two has elevated his game in recent months, winning his first major at the U.S. Open, followed by a World Golf Championships victory and a triumph at the BMW Championship in his last start. More...