“He has the weapons he’s going to use — his serve, his forehand. Most players are very focused on what’s happening with themselves, on their side of the net. I’m much more focused on what’s happening on the other side of the net. So the tactics are very important to me, and Jan is very good with this, especially with the help of the video.”

Simon said De Witt’s video had been particularly useful before his match against third-ranked Andy Murray in the Round of 16 in Madrid in May. Murray had dominated Simon in the past, but Simon pushed him in Madrid, losing in a third-set tiebreaker.

“I had lost 10 times to Murray, and Jan wanted to show me in what patterns I had lost points, what I needed to avoid and how I should try to direct play, and it helped me enormously,” Simon said. “Doing a video is easy; all you have to do is film something and cut it into parts. But the hard part is to know how to use it intelligently. That’s what’s interesting, and that’s what the coach’s job should be. He should give only the essential to the player.”

Simon said statistics could be dangerous. “I’ll give you an example,” he said. “The data might tell us that if I go to net attacking a certain player’s backhand, I win 80 percent of the points. But if you play the match and go every time to the backhand, you are not going to win 80 percent of the points anymore because the player is going to know that it’s coming always to the same place.”

Coaches and tennis parents have been filming matches and practice sessions on a regular basis since the advent of the video camera. But one of the first tennis coaches at the elite level to make use of video to dissect opponents’ patterns was the Australian Darren Cahill when he was coaching Lleyton Hewitt and Andre Agassi in the early 2000s.

He received his inspiration from Australian rules football, which his father, John, played and coached at the professional level. Cahill said he bought a system called SportsCode from the Australian Football League.