Story updated 17 November

What happens when the game’s best returner suddenly becomes one of the best players at holding serve? Things get scary. Quickly!

Since Wimbledon, Novak Djokovic has been holding serve more than 9 out of 10 times. He continues to break serve almost once every three times. Any mathematician will tell you those are winning numbers.

Having started the year with a 6-6 match record, Djokovic has completed the greatest in-season turnaround by a player to finish the season World No. 1 in ATP Rankings history (since 1973).

Brad Gilbert, the former World No. 4, leading coach and now insightful commentator, traces Djokovic’s resurgence to his epic semi-final win over Nadal at Wimbledon. And, in particular, the Serb’s serving performance that day.

“I thought that was his best-serving match in a long time and that match was the impetus to where he is now. His serve has been the huge difference in his game as he’s gone on this run,” Gilbert says. “He’s not serving massively bigger but, like Rafa, he’s a good spot server who hits the corners. He's hitting service winners and winning a higher percentage of first-serve points.”

Prior to Wimbledon, Djokovic was winning 84.4 percent of service games in 2018. But since Wimbledon the Serb had held serve 90.9 percent of the time leading into Nitto ATP Finals.

At the Rolex Shanghai Masters last month, Djokovic won a title without dropping serve for the first time in his illustrious career. And after winning all 36 service games through the semi-finals of the Nitto ATP Finals this week, Djokovic has the opportunity to double down in London when he takes on Alexander Zverev in Sunday's final.

Djokovic's vanquished semi-final opponent Kevin Anderson said tonight that he had never seen the 31-year-old serve so well, but the Serb says his delivery can get even better.

"It's still ongoing work," Djokovic said Saturday night. "It will continue because I feel like I always can improve that shot. Obviously glad that my opponents feel like I'm improving in my serve, because it is ultimately the most important shot in the game.

"I thought I was also backing up the serve with the first shot in the rally very well through the entire week. That allowed me to kind of protect my service games, win them all so far in the tournament."

On a full-season basis, only five players have held serve at 90 percent or better in 2018: John Isner, Ivo Karlovic, Roger Federer, Milos Raonic and Nick Kyrgios. (It must be noted that those marks include the clay season, during which it can be tougher to hold serve. Djokovic’s 90.9 percentage rate has been achieved on grass and hard.)

Caveats aside, Djokovic’s serving numbers underpinned his remarkable 31-1 record from the start of Wimbledon up to his loss in the final of the Rolex Paris Masters to Karen Khachanov. Gilbert believes that the Serb’s second-half run will continue, if not accelerate, in 2019.

“I think he's about to dominate,” Gilbert says. “The freight train has started and it’s full steam ahead.”

Gilbert was coaching Andre Agassi in 1999 when the American worked his way back from a low of No. 14 in May to win two majors [Roland Garros and the US Open] and finish on top of the ATP Rankings. Prior to this year, that same-season comeback was the biggest by a year-end No. 1.

“Novak’s Wimbledon breakthrough and his 31-2 [match record] turnaround totally reminds me of what Andre did in '99 when he won the French, got to the final of Wimbledon and won the US Open. I think Novak is looking at a monster 2019. I could see him winning Australia and all of a sudden he's in play for his second Djoker Slam.

“He’s tying Federer and Connors with five year-end No. 1 finishes. Beating Sampras' six year-enders, finishing his career with 45 Masters 1000 titles… all these things are possible. But right now I'm sure he's just focussed on finishing the year strong and winning the Nitto ATP Finals.”

Did You Know?

Djokovic's 23 aces against Nadal in his five-set victory at Wimbledon this year were a career-high for the Serb.

- Story was first published 11 November.