Jason Stacy's C.V. covers a lot of bases.

The American has a martial arts background and has worked in massage therapy, sports therapy and strength and conditioning for some 25 years.

From 'soccer' players to Olympic development teams, from swimmers to ballroom dancers, Stacy's expertise in coaching and hands-on fitness has taken him all over the globe.

"I've helped athletes get to world No.1 or become world champion in four sports now. Two different martial arts – jiu-jitsu, judo, then swimming and tennis."

That tennis player is Aryna Sabalenka.

Stacy's first tennis prospect was Dmitry Tursunov. When the former world No.20 retired Tursunov moved into coaching, working with Sabalenka in two stints between July 2018 and August 2020.

In comes Stacy as performance coach: an engaging, expressive bundle of energy, who has become the glue for Team Sabalenka.

"She says I've been with her way longer than anyone else, any other coaches," Stacy told wimbledon.com.

"There's been a lot going on over the years, inside of tennis, outside of tennis, I've tried to keep all the pieces together as best as possible. It's a team effort for sure."

Lead coach Anton Dubrov takes the technical side and in their time at the helm Sabalenka has topped the world rankings and lifted two Grand Slam trophies at the Australian Open (2023 and 2024). She is an ultra-consistent force, with a tour-leading game.

"She's willing to do the work no matter what. It's a big part of what got her through the early days. She's a fighter. There's that fire inside of her," Stacy said.

"She's got that X-factor, but also she is still aware and wanting to improve. She's super loyal - she understands where she came from, how she got here, and what she needs to do to stay here."

Since a first Grand Slam match win at Wimbledon 2017, Sabalenka has become known for her raw yet unpredictable power, a whirlwind within the confines of a tennis court.

Stacy set to work.

"When I met her she was a strong girl, a lot of power, but it wasn't controlled, there was no intention or purpose behind it. She just knew how to hit the ball super hard," Stacy recalled.

"She was doing twice as much work, for half the outcome, now she's doing half the effort for twice the outcome. She's much more efficient, much more co-ordinated – that was the physical movement side.

"The other part was the way that she used to breathe. It was very up heavy, mouth breathing, up in her neck, she was always having shoulder and neck issues, which was coming from getting frustrated the whole time.

"I taught her the mechanics of breathing, got her to strengthen her respiratory muscles properly so she could control when she needed to lower her heart rate, whether she's trying to clear her head and focus more, be in the moment, which has developed that calm, fierceness she has these days.

"Just to manage her emotions was the other part, which is related to the movement, the breathing. Energy management is behind all our decision making. It's been a real trial and error, working out which tools work with her, which methods connect with her and just evolving those."

Stacy's job is to make sure that physically and mentally, Sabalenka is ready to do whatever Dubrov wants her to do.

"Another big part of my role is to make sure we have the right people, doing the right thing, at the right time. That's where I joke that I'm the 'babysitter' of this team. That goes as far as how people are speaking, what their body language is like, before, after a match," he said.

"Gavin Macmillan (biomechanics coach) has been a huge help at a technical level, he's made a big difference from getting to the semis to winning Slams.

"From Gavin she understands if she misses a ball, why. That gives her a calmness to problem solve. He's someone we'll bring in and out, we're constantly working on things and she's trying to develop new habits, build that awareness. Understanding the technical details is giving her control."

Rewind to the Australian Open this year and Sabalenka began the tradition, which went viral on social media, of signing and doodling on Stacy's head just before a match.

The 'signature' tradition will continue into SW19; 'fun' is the buzzword for team Sabalenka.

"If it's a grind, what's the point? It's hard for all of us, we've got to make sure as a person, she enjoys this journey. We don't want her to look back, miserable with lots of money.

"It happens a lot, they've destroyed themselves mentally and physically. There's always a time to get serious, but you've got to have fun!"