He pair fought a tight third set, watched by their celebrity coaches, former champions Boris Becker and Goran Ivanisevic from the player's box.

Djokovic hit the ground three times during the tiebreak, on one occasion tumbling spectacularly into the net.

"It was a tough five-setter. Coming in I knew Marin would play aggressively," he said.

"He raised his game but I allowed him to come back into it. I was too passive on my strokes and he used his opportunities, but I managed to find the right pace when I needed it."

Djokovic donned a new pair of shoes early in the fourth set, upped the pace and raced into his 23rd semi-final, where he will meet 23-year-old Bulgarian Dimitrov.

"After I changed my shoes I played well," a smiling Djokovic said.

"I had just a better grip. I had better movement. Maybe it was just mental, but anyway, it worked."

He added he would keep the lucky shoes to play Dimitrov.

"It was a big win for Grigor. He's on fire this last six months," Djokovic said.

"The fact that he hasn't lost a match in the grass court season this year says enough about his quality.

"Also winning against Andy. I'm sure many people look at him as a potential grand slam winner. Maybe here, maybe in the grand slams to follow."