“It’s high percentage for me to go big under pressure,” Kyrgios said in Miami this year after losing a classic three-setter to Roger Federer that was full of second-serve risks. “Sometimes it comes off, and sometimes it doesn’t.”

It is not just the younger players who are re-engaging in swordplay. Sam Querrey, the American veteran who is having his finest season at age 30, began hitting more powerful second serves than usual in Shanghai this month.

“Sam threw it in, tried it, and it worked,” said Craig Boynton, Querrey’s coach. “My conversation with anybody that is going to do that, and I think Nick does it far and away more than anybody else, is what is your consistency rate? And what is the score line? When you are down 15-40 or 0-30 you are really rolling the dice, but if you are 30-0, 40-15 up and you want to throw a different wrinkle in, it’s a different equation.”

It is also a more favorable equation on a hard court or in an indoor tournament like the Paris Masters that begins Monday. Wherever it happens, a second-serve ace does seem to have a bigger psychological ripple effect than a first-serve ace. It sends a message that an opponent is unpredictable but also bold.

“Absolutely,” said Paul Annacone, who has coached Sampras and Federer. “When you’re helpless because of a first serve, it’s one thing but it’s another thing when all of the sudden you are playing Kyrgios and it’s 3-3 in the tiebreaker, which it was against Roger in Miami, and he hits a second-serve 131 miles per hour up the T that is unreturnable.

“To me, you either go, ‘He’s crazy.’ Or you think, ‘Now I’m not even getting a look at his second serve in big moments?’ That’s a huge impact. No. 1, you have to have confidence to do it. There’s a big difference between doing it out of desperation and doing it strategically. When Kyrgios does it, I don’t have a problem. People will go, ‘Oh, it’s a bailout.’ But he’s a great server. He believes he’s going to make that second serve, just like Pete did.”