At first glance, Novak Djokovic's four-set Australian Open win over Enzo Couacaud would seem like a minor bit of turbulence for the 21-time Grand Slam champion. However, the match was anything but. Djokovic battled past a heckler who appeared to enjoy one too many adult beverages while also tweaking a nagging hamstring injury in his left leg.

At one point, the mental roller coaster appeared to be getting to Novak Djokovic, who wanted the heckler removed from Rod Laver Arena. Djokovic was heard saying, “The guy's drunk out of his mind. … He's been provoking. He just wants to get in my head.”

An irate Djokovic told chair umpire Fergus Murphy that the heckler was “not here to watch tennis” at the Australian Open.

Novak Djokovic got some measure of revenge, blowing a kiss to the heckler in the crowd.

But the heckler may have been the least of the nine-time Australian Open champ's worries.

Djokovic, who entered the tournament with health concerns, appeared to tweak his hamstring injury during the second set of the match, requiring a medical timeout.

While the Serbian tennis star was on cruise control after the timeout, dropping just two games en route to his 23rd straight Australian Open match victory, his comments on the injury after the match were concerning, to say the least.

He said the injury is “not good at all”, though he made sure to note that it was better than his last match.

Novak Djokovic fans will have to hope he can power through the injury.

But in the meantime, they can take solace in the fact that a heckler and an injury were not enough to overcome one of the sport's most mentally strong players.

Novak Djokovic summed it up best, per ESPN.

“It was a lot happening tonight.”