Djokovic struggled with a left shoulder injury in Wednesday’s second-round win, but the top seed looked far more at ease against 111th-ranked Kudla as he advanced to a showdown with 2016 champion Stan Wawrinka.

“I managed to play almost pain-free. That’s a big improvement from the last match,” Djokovic said.

“Obviously I didn’t know how my body would react and I’m glad to just finish the match tonight. I’m not going to go into medical details, but it was definitely bothering me the last couple weeks.”

“I didn’t practice yesterday. I just wanted to give myself time and do everything possible to recover,” he added.

Djokovic is attempting to become the first back-to-back men’s champion here since Roger Federer won five titles in a row from 2004 to 2008.

He will meet Wawrinka, the man who beat him in the US Open final three years ago, for a place in the last eight.

“We’ve had some great battles over the years, all over the world and especially here,” Djokovic said of his upcoming clash with the Swiss three-time Grand Slam champion.