'I've played this year so far only once in first four matches on Centre Court.
It will be Djokovic's first Grand Slam semi-final since the 2016 US Open as he continues his bid to return to the top of the game.
At the start of the second, Djokovic was putting Nishikori under enormous pressure again, but the Japanese held firm on serve in a 10-minute game.
"I've been building the last couple of weeks on the level of tennis that I've played the last couple of month, the last couple of clay-court tournaments and Queen's".
Israeli military says it shot down a Syrian drone Russian Defense Minister Sergei Shoigu said Moscow is ready to discuss the issue of supplying Syria with the S-300 missile system. Israel has been on high alert as Syrian President Bashar al-Assad's forces advance on rebels near the Golan Heights and Jordan.
"I am peaking at the right moment".
Yet the 22-year-old, playing in the last 16 for the second successive grand slam, saw his hopes severely hindered by mistakes and a sliced forehand wide gave Djokovic a pair of break points - only one of which he needed.
"You're saying in the point if I toss my racket like this I'm ruining the court?"
It didn't show in Djokovic's play, though, as he embarked upon another swing of four games in succession, holding Nishikori to three points in his next two service sets as he soared into a 4-1 lead.
The 2011, 2014 and 2015 champion was clearly unsettled by the dispute, quickly surrendering the set. The world number 40 was unable to mount a response this time and evidence fortune was in the Serbian's favour came on his second of two set points when a Khachanov slip enabled him to take a 2-0 lead in the match.
"Double standards, my friend".
Ramos then hit Djokovic with a time violation warning for taking too long to serve in the seventh game of the fourth set.
Nishikori, playing in his first quarter-final at the All England Club, was bidding to become the first Japanese man to make the Wimbledon semi-finals in 85 years.