It’s not quite a first serve. It’s certainly not a typical second serve. Then what is it?

It’s a hybrid of the two, and Novak Djokovic has brought it out to play in 2020.

The 16-time Grand Slam champion has added an eye-catching 6 mph this year to his average second serve speed. Through the first four rounds at this year’s Australian Open, his average second serve speed was up to 104 mph. By way of comparison, his average first-serve speed for that timeframe was 118 mph.

Amazingly, he’s not double faulting more with the increase in speed. Through the quarterfinals, Djokovic has only 12 double faults. Last year through the quarterfinals, he had committed 13. And not only has he increased the speed, but Djokovic is also showing an unconventional style for the type of stroke he hits for a second serve and where he directs it.

Players commonly hit a slice on a first serve. It’s a faster, cutting shot, and because of the sharper trajectory, it’s a more attacking — and riskier — serve. Players more often reserve a kick serve for a second serve. A kick serve offers a safe margin over the net, and the heavy topspin sends the ball jumping sharply off the court. But a kick serve is not a fast serve.

The faster, hybrid second serve that Djokovic has often deployed at Melbourne this year isn’t a kick serve — it’s a slice, according to coaches and analysts examining it.

“It’s tricky. Djokovic’s service motion has always been unusual, but this service is more slice,” said Shane Liyanage of Data Driven Sports Analytics, which provides scouting for ATP players.

Djokovic’s new second serve is also confounding opponents with its bold and unconventional placements.

The service box is divided into thirds when measuring serve placements: “Wide” serves are placed closest to the sidelines; “body” serves land in the middle of the service box, at the returner’s body; and “T” serves land along the center stripe of the service box. Conventional wisdom in tennis holds that most players have stronger forehands than backhands. Because of this, a kick serve to a player’s backhand is considered the ultimate safe, defensive strategy. It’s the gold standard for the second serve.

In Melbourne, Djokovic is more often doing just the opposite — hitting to his opponents’ forehand on second serves.

According to data from Infosys, when Djokovic had a second serve from the deuce (right) side of the court in the first four rounds of the tournament, he hit the most to the out-wide location — 22 out of 40 times. For right-handed opponents, three of Djokovic’s first four opponents, the out-wide spot would be to their forehand.

In the advantage (left) court, a similar pattern emerged in the first four rounds. Djokovic hit most of his second serves (28 out of 45) to the T location — also to right-handed opponents’ forehand.

So is this new serve working?

In the first four rounds in Melbourne, when Djokovic hit a second serve to those locations — wide in the deuce court, T in the ad — he went on to win the point 74 percent of the time, according to Infosys. That serve placement has proven a stunning formula for success.

But what about his overall winning percentage on second serve points? In 2019, he won 57 percent of his second-serve points at the Australian Open through four rounds. This year, that number is outpacing his old percentage at 60 percent through four rounds. Roger Federer and Rafael Nadal are tops in second-serve point success over the past year, with 59.4 percent and 59 percent of those points won, respectively.

Djokovic is also winning matches. Through five matches in Melbourne, he has dropped only a single set. He faces Federer in the semifinals at 3:30 a.m. EST Thursday.

Djokovic isn’t the first player to use a faster second serve to good effect. Players like Nick Kyrgios have been known to employ that tactic to surprise their opponents. A returner is more likely to make an error when expecting the traditional, slower second serve, while something that looks more like a first serve comes out of nowhere.

But Djokovic is not using this faster slice second serve as a surprise tactic — he’s hitting it regularly, according to data from Infosys. Through the first four rounds, the number of Djokovic second serves that topped 105 mph was 52 out of 85. That’s 61 percent.

Kyrgios averaged about 100 mph on his second serve at the Australian Open, slower than Djokovic’s average. Djokovic’s emergence in this category is even more remarkable when you consider that he has not been known as an exceptional server.

If you’re returning against this new-look Djokovic second serve, what do you do? For one thing, prepare for the serve out wide in the deuce court and up the T in the ad court. But also, consider going for more on your own second serve. Clearly, it’s an effective tactic.