WINSTON-SALEM, North Carolina, Aug 27 AP – Steve Johnson reached the ATP Tour’s Winston-Salem Open semi-finals when Taiwan’s Yen-Hsun Lu withdrew because of a back injury.

Lu was hurt late in the third set on Wednesday in his 7-6 (7-1) 1-6 7-5 quarter-final 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 disc 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 soreness, and I really couldn’t do anything natural. It really didn’t make sense to go on the court and play. It’s not smart.”

Johnson is seeded 13th and the lone American remaining in the final tuneup before the US Open. He will play either qualifier Pierre-Hugues Herbert of France or Pablo Carreno Busta of Spain.

Johnson reached his third career semi-final and second this season. The two-time NCAA champion at South California made his last semi-final appearance three weeks ago in Washington.

“It’s never the way you want to win,” Johnson said.

“Rendy’s (Lu’s nickname) a great competitor, and I was looking forward to getting a chance to play. Unfortunately for him, his back isn’t feeling 100 per cent. With the U.S. Open right around the corner, he didn’t want to jeopardise something today for the following week. Now I just take today, and get ready for tomorrow.”

In the night session, second-seeded Kevin Anderson of South Africa faces eighth-seeded Borna Coric of Croatia, and sixth-seeded Thomaz Bellucci of Brazil plays Malek Jaziri of Tunisia.