Novak Djokovic has become the latest player to take issue with the new automated shot clock.

The 24-time Grand Slam champion claimed the tour changed the rules mid-season without informing players.

Since June, the ATP has been trialling a system which means the 25-second countdown to serve begins exactly three seconds after the last point. Previously umpires had the discretion of when to start the shot clock.

But the world No. 4 has not played an ATP-sanctioned event since May, so the Shanghai Masters is the first tournament in which he's experienced the new automated system. And he's not a fan.

Djokovic initially complained about the countdown when he received a time violation during his opening match against Alex Michelsen. Chair umpire Mohamed Lahyani explained that he could no longer control the shot clock.

And the 37-year-old aired his grievances again on Wednesday as he faced Roman Safiullin in the last 16. Djokovic seemed to ask Nacho Forcadell, the chair official for the match, about the rule.

"It’s automatic, three seconds, Novak," the umpire replied. Djokovic then went on an impassioned rant as he also brought up another tweak to the rules - ball kids are now allowed to give players their towels after it was stopped four years ago.

"No, I get it. I get it’s not up to you. But the rule change is unbelievable," he vented.

"I mean for four years we've had this situation where we can't get the towel, right? Ball kids are doing their best but they’re not being trained. Without even notifying any players, you start this new rule. I mean, it's incredible. Honestly."

The world No. 4 continued the conversation into the next changeover, where he tried to learn more about the automated shot clock.

"First time that you are having this situation, right?" he asked Forcadell. The umpire replied: "No, we already had it. I think we started grass season."

Djokovic appeared surprised. "Grass season? ATP?" he continued before Forcadell confirmed the automation was only used at tour events, not at Grand Slams or ITF-sanctioned tournaments.

But Djokovic's last ATP event was the Geneva Open. Since then he's played three Slams - the French Open, Wimbledon and the US Open - and two tournaments representing his country - the Olympics and Davis Cup.

"For me it’s first time. I feel like if we all agree that we start the season this way, we’re not mid-season experimenting in a Masters 1000 event, you know what I mean?" he added.

Djokovic isn't the only one who doesn't like the new rule. When it was first introduced during the grass swing, Carlos Alcaraz vowed to discuss the issue with the ATP after claiming it was "bad for players" while competing at Queen's.