Johnson, Herbert Reach Winston-Salem Semis

WINSTON-SALEM, N.C. — Steve Johnson reached the Winston-Salem Open semifinals when Taiwan's Yen-Hsun Lu withdrew because of a back injury.

Lu was hurt late in the third set Wednesday in his 7-6 (1), 1-6, 7-5 victory over South Korea's Hyeon Chung at the Wake Forest Tennis Center. He was treated after the match and Thursday morning. The pain and cramping persisted during practice, forcing his withdrawal.

"There's a disk that had some inflammation inside, and the inflammation got into the muscle and got it tight," Lu said. "It was really affecting my serve. We're all looking forward to next week, but I'm still upset.

"We did everything we could with the ATP (trainers). There's still some…