How data-driven coaching helped Angelique Kerber to latest crown

When Angelique Kerber hired Wim Fissette at the end of 2017, she was "curious" as to what they could achieve together.

Seven months later and any questions she had have been answered. Kerber is a Wimbledon champion. The German, who won two Grand Slam titles in 2016, dropped out of the top 20 last year. But she was not content to led the slide linger. Kerber and coach Fissette sat down to discuss her goals.

"Last year when I started with Angie, I looked at all her stats from the year before, and I saw she was serving 75 percent to the backhand," the Fissette told ESPN.com at Wimbledon.

"So I told her, that is something that needs to change, the percentage going to the forehand needs to be much higher. After the first month, she played in Australia, we saw the stats and we saw immediately how much she improved."

Fissette is one of a number of leading coaches on tour who has embraced the WTA's partnership with SAP, the Germany-based enterprise software company.

Using Hawk-eye technology and the umpire's score pad, SAP produces live stats available during matches using Tennis Analytics for Coaches, a tool that is often shown when coaches come onto the court during WTA matches. After matches, coaches can consult the Tournament Performance Centre tool to get even more detail.

Having coached Kim Clijsters, Victoria Azarenka, Simona Halep and Johanna Konta, Fissette has a resume few other coaches can equal. As one of the coaches consulted by the WTA and SAP when they were putting it together, Fissette says the SAP stats have "changed my life."

"Instead of waiting two hours on the court, to watch one match for two hours, to have this little amount of data, now I can go home, sit at my computer or wherever I want, drink coffee at Starbucks and can start my analysis, and I am a much better coach than I was before," he said.

"Before we had this, I went to watch matches with a piece of paper, and I was putting dots where the first serve landed and stripes for the second. Now we have this, within 20, 30 minutes, I can look at the stats of one player, let's say, of all their matches on grass, on hard court. I can look at 10 different matches and compare them.

"I call this my assistant coach, because at the end, there is so much data and I have to decide what is important for me, and what is important for my player going into one match. You can overload your player with stats, and it's about picking maybe two or three really important things to take into a match, and it's of course the job of the coach to find the right ones."

Coaches also have to understand how their player's minds work, so what worked for Clijsters may not be what worked for Azarenka. Kerber, again, was different.

"Vika, she wanted to have lots of information, the more the better," Fissette said. "She could really use it in a match. Angelique is a little different because she plays more with feelings, emotions, intuition, so I have to be careful not to give her two much. Let's say two, three, very important things and not more.

"Kim, she was 100 percent intuition player, on feelings. With Angie, she's more a counter-puncher, and it's very important to see where serves are landing, what does she do in this situation, so it's more a tactical game."

When testing the tool, the WTA and SAP overcame a number of challenges, from making sure the tablet that housed the program worked when exposed to hot temperatures, to reducing the glare of the sun and ensuring the connection was strong enough.

Trust between player and coach is paramount to success in any sport. That players can now see the stats themselves means they are more unlikely to question their coach. "It's a complete change of communication, a lot more trust coming from the player toward the coach," Fissette said.

Of course, since every coach has access to the same range of stats, there are few secrets in terms of strategy, at least so long as the respective coaching teams do their research.

On-court coaching is allowed on the WTA Tour, but not at Grand Slams events. Richard Lewis, the CEO of the All England Club, said this week this he does not believe in the merits of on-court coaching, and it doesn't look like this will change anytime soon. For Lewis, and others, the beauty of tennis is its gladiatorial nature, problem-solving an art in itself.

"As a coach at Grand Slams, you have less influence during the match, but I always try to prepare my player the best and prepare for anything that can happen during a match," Fissette said. "It's up to the player. It's not like I can program my player and she does exactly that. The player still has to make big decisions in the match and be responsible for their game. I could say, 'Hit the serve down the T at 200 kmh' and probably you're going to win, but you have to do it, right? That's always going to be the most important thing."

Fissette has now coached his way to three major titles. He and Kerber both need only the French Open to complete the full set. Perhaps the stats will unlock the secret.