Paris - Michael Chang said on Monday that he expects more players to use underarm serves, 30 years on from "the only one of his career" in a famous victory over Ivan Lendl at Roland Garros.
The American, then 17, stunned Lendl in a dramatic fifth set in the fourth round before going on to win his only Grand Slam title.
Players this season have started to use the controversial tactic more regularly, including Australian star Nick Kyrgios and Kazakhstan's Alexander Bublik.
"Back then, you didn't have guys returning so far, so deep. Rafa (Nadal) is so far back, Dominic (Thiem) is far back, (Daniil) Medvedev is so far back," said Chang, who now coaches Japanese seventh seed Kei Nishikori, who faces Rafael Nadal in the quarter-finals at Roland Garros on Tuesday.
"So the guys are starting to go 'Well, if the players are willing to go that far back, what's the good shot to hit against them, a drop shot. So why don't I do that on my serve?'
"Bublik did it three times against Dominic and I think he won two of the three.
"But if they're 15 feet behind the baseline, I think that does warrant a thought of how effective that serve can be. If you hit it well, it can be really effective."
Lendl was visibly shocked by Chang's underarm serve in 1989, but he says it wasn't a pre-planned gameplan.
"It literally only crossed my mind for one or two seconds and that was it," he added.
"I felt like I was losing my serve and I was about to lose my serve again. I couldn't serve my first serves, so I felt like I needed to try something different to try and win points. It's the only time I've ever done it, ever in my entire career.
"It's part of the history I think here in Paris at the French Open. My match with Ivan is a match that is difficult to describe.
"It was an incredible match. It's a story you can tell your children before they go to sleep. Most of those stories are not true, but this one happened to be true."
Eleven-time champion Nadal holds a 10-2 winning record over Nishikori, and has four victories from as many meetings on clay.
But Nishikori has troubled the Spaniard on clay in the past, especially when he was leading Nadal in the 2014 Madrid Open final by a set and a break before suffering a back injury and retiring in the deciding set.
"With Kei, you take advantage of the strengths that you have, which is his ability to hit great shots," said Chang.
"Kei is probably one of the most talented players out here. He knows how to play and he's beaten the best players in the world."
Results from the ninth day of the French Open on Monday (x denotes seeding):
Novak Djokovic (SRB x1) bt Jan-Lennard Struff (GER) 6-3, 6-2, 6-2
Alexander Zverev (GER x5) bt Fabio Fognini (ITA x9) 3-6, 6-2, 6-2, 7-6 (7/5)
Dominic Thiem (AUT x4) bt Gael Monfils (FRA x14) 6-4, 6-4, 6-2
Karen Khachanov (RUS x10) bt Juan Martín Del Potro (ARG x8) 7-5, 6-3, 3-6, 6-3
Kei Nishikori (JPN x7) bt Benoît Paire (FRA) 6-2, 6-7 (8/10), 6-2, 6-7 (8/10), 7-5
Madison Keys (USA x14) bt Katerina Siniakova (CZE) 6-2, 6-4
Ashleigh Barty (AUS x8) bt Sofia Kenin (USA) 6-3, 3-6, 6-0
Simona Halep (ROM x3) bt Iga Swiatek (POL) 6-1, 6-0
Amanda Anisimova (USA) bt Aliona Bolsova (ESP) 6-3, 6-0