Tennis coaches have long used post-match data to help their players improve and understand the strengths and weaknesses of their opponents.
Such statistical analysis is usually a long, drawn-out process involving considerable guesswork — and of little help in the middle of a match.
Belgian tennis coach Wim Fissette recalled looking for patterns in the game play of his charges to pinpoint what areas needed improvement. Working through three or four matches took as much as 10 hours.
"I took a piece of paper and I made dots of where the balls were landing and of course it was not [very accurate]," Fissette, who has coached top players including Kim Clijsters, Simona Halep and Victoria Azarenka, told CNBC at the sidelines of the WTA Finals championship in Singapore.
He recalled a game in 2010 when he coached Clijsters against Azarenka.
Fissette knew, from watching previous games, Azarenka tended to hit her backhand shots wide when she had the advantage on a tie break. "That's what I told Kim," Fissette said.
Clijsters was skeptical; Azarenka served wide and won a point; and another. Clijster's skepticism turned into surprise. "She looked at me. The third time, she was ready and she won the point," he said.
Things have gotten a lot easier for coaches since then. Current technology allows for the collection of vast amounts of data in real time and companies are already creating tools that can carry out instant analysis.
In 2015, German software firm SAP provided real-time data analytics based on information collected from match umpires and ball tracking cameras. Coaches could access the information on WTA-approved devices and bring to their players during coaching breaks.
For example, when Angelique Kerber begins her semi-final match at the WTA Finals in Singapore this weekend, her coach can theoretically show her real-time data on her opponent's strengths and weaknesses.