Whacking the cover off a tennis ball was once Plan A, B and C for Naomi Osaka but the hard-hitting U.S. Open champion has been trying to add dimensions to her game as she searches for a second consecutive Grand Slam title at the Australian Open.
The fourth seed has had to mix things up during a grinding progression to the last eight at Melbourne Park and needed to rally from a set behind for the second match in succession to beat 13th seed Anastasija Sevastova 4-6 6-3 6-4 on Monday.
The Japanese player next meets sixth seed Elina Svitolina for a place in the semi-finals.
Osaka is one of the fiercest shot-makers in the game, as Serena Williams found to her cost in the final at Flushing Meadows, but the 21-year-old has also thrown more drop-shots into her game and is less wary about approaching the net.
The refinements have made her a better problem-solver when under pressure and helped in the course of overhauling Sevastova and third-round opponent Hsieh Su-Wei, according to her coach Sascha Bajin.
"From the very beginning, when I started with her, I always tried to tell her that there are so much more different types of pressure than just blasting the ball," Bajin told reporters at Melbourne Park on Monday.
"So you can hit angles, different types of spins, a drop-shot coming in, getting 50 balls back in a row is putting pressure on the opponent," the German added.
"So I wanted her to understand that. And knowing that she did have already so much power, it was very obvious she just had to do more of the other stuff. I always want her to play her game first and start trying to win these matches as easy as she can. But if something isn`t working, you need to have a plan B, plan C. That`s what we have been trying to work on in practice," she added.
Bajin, a former hitting partner to Williams, Victoria Azarenka and a host of other top names, was given the 2018 WTA Coach of the Year award for guiding Osaka to her maiden Grand Slam title.
Her triumph was marred by a huge row between Williams and the chair umpire in the final after the American was issued a code violation for on-court coaching, which is permitted at WTA events but still not allowed in the main draw at Grand Slams.
Bajin, however, is left cold by the idea of on-court coaching in all matches.
"My personal opinion is I don`t like it. I don`t like on-court coaching, I don`t like coaching from the sidelines," he said.
"I think it takes away the purity that tennis has. My father put me out there on the court in order to become more independent, to learn how to handle problems, to learn how to be by myself so that nobody can help me. And I think that parents still do that for their kids. That's why they want them to start this sport because it's something special. And I wish we would keep it that way, and that's just my opinion. Not changing it for the viewer or something, you know, to make it more interesting," he concluded.