Despite having a spiritual guru in his camp these days, Djokovic has been anything but serene lately and once again the defending champion cut an angst-ridden figure for long periods of a tense clash in the prestigious season-ending event at London's O2 Arena.
Djokovic had reacted furiously after being grilled by the media about a potentially dangerous incident when he slammed a ball into the stands during his win against Dominic Thiem on Sunday.
This time, the world No 2 grumbled over camera flashes from the crowd and held a finger to his lips to urge them to be quiet, while moaning when Raonic tried some gamesmanship by taking his time tying up his shoelaces at a key moment in the first set tie-break.
But, to his credit, Djokovic handled everything a fired-up Raonic threw at him to ensure he remains on course to win the Tour Finals for a fifth successive year and record-equalling sixth time in total.
The 29-year-old, who has now won 20 of his last 21 matches at the Tour Finals, would also regain the No 1 ranking from Andy Murray if he leaves south London with the silverware.
"I managed to hang in there mentally and stay strong and believed that the opportunities would come and that I could take them," Djokovic said.
"Milos was hanging in there and only one or two points separated us in the second set.
"It could have gone either way this match. He's such a strong player and has got firepower."
With Austria's Thiem having kept alive his hopes of reaching the semifinals with a 6-3, 1-6, 6-4 victory over Gael Monfils earlier on Tuesday, Djokovic knew a win would seal his last four berth with one match still to play.
