When the Croatians faced off against hosts Russia in their quarter-final many Serbs who gathered to watch in cafes in central Belgrade were backing the Russians rather than their neighbours from the former Yugoslavia.
With South African Kevin Anderson taking nearly 3-1/2 hours to tame French showman Gael Monfils in a four-set thriller in the previous match, Djokovic was left with about two hours of daylight to complete his match against Karen Khachanov if wanted to avoid coming back on Tuesday again.
" I thought it was unnecessary to get the warning". He last featured in the semi final of 2016 US Open.
"It took me two or three months and that was frustrating that I wasn't able to perform the game that I was used to and the level of tennis I wanted to play". Djokovic broke Nishikori's serve seven times, and finished with six aces.
Later in the match, Djokovic was clearly frustrated and complained of "double standards" when Nishikori was not punished for a racket throw. "I think confidence is back for him".
Nishikori, playing Djokovic on grass for the first time and seeking to end a 12-match losing streak against the Serb, held his own in the third set before running out of steam.
Yet Djokovic appeared to have more control over the ball than his opponent, and when the set was tied at 3-3, he found another gear.
He also spoke about his anger that he displayed during the match, which is very uncharacteristic of him, he said, " Sometimes it fires you up, so...
"It felt like it was getting better and better as matches and time went on". I really do. I think with the performances I've had, I deserve to be in the semi-finals.
Eight-time champion Federer has already won more Wimbledon singles titles than any other man, but was aiming to equal Martina Navratilova's all-time record. "In the same time, I'm trying to use the experience and memories that I had on being in final stages of Grand Slams, just take things very simple, day by day...not get ahead of myself too much". "Djokovic is a national hero and I thank him - but support Croatia, how can he not be ashamed?"
"I want to use today's result as a spring from which to aim for a final place".
But the second seed stayed alive by taking the fourth set before the gripping drama continued in an electrifying deciding set in which both players were left diving after volleys and slipping over as they chased after blinding winners.