After seeing off big servers Kyle Edmund and Karen Khachanov, he faced Nishikori, who had recovered from his own serious injury to hit peak form in reaching his first Wimbledon quarter-final.
" I thought it was unnecessary to get the warning".
"I think it's not fair, but it is the way it is in the midst of the emotions of a match".
With the Japanese serving to stay in the match, Djokovic wrapped things up after 2-1/2 hours on the first match point to secure his first Wimbledon semi-final since 2015. I feel like a lot of aspects of my game can give him a lot of trouble'.
After racing through the first set, Djokovic was handed his first code violation for unsportsmanlike conduct after bouncing his racquet into the grass in frustration at squandering three break points in the third game of the second set.
The South African is through to the last eight for the first time, and he said: 'Playing somebody like Roger Federer is going to be a great experience.
It nearly looked like Djokovic ended up giving Nishikori the point on the ensuing backhand, because when you've earned it you've earned it. Djokovic has been looking like his old self again this Wimbledon, but you have to think there's a voice in the back of his head wondering why this keeps happening to him.
"You're saying in the point if I toss my racket like this I'm ruining the court?"
The Argentine, who leads the stubborn baseliner 4-3 in previous encounters, levelled on his second break point and it went to 5-5, but Simon broke again to take the first set off Del Potro in the tournament so far. It's a big chance for me to face Rafa. I know how I threw the racquet.
The semi-final will be the 32nd of Djokovic's Grand Slam career but he has had to fight to get there.
Djokovic has got his wish as he will take on the world number 24 Kei Nishikori on Centre Court, while Federer will take on Anderson on court number one.