The eight ways to force an error in tennis are: consistency, direction, depth, height, spin, power, court position and time (taking time away for the opponent to prepare for a shot).
The history of the unforced error can be traced to 1982, when Leo Levin, who played at Foothill College in Los Altos Hills, Calif., decided to chart his teammates’ matches. He tracked the errors they were making and the errors their opponents were forcing them to make.
“That concept of forced and unforced errors kind of came into being around that time, and then I got hired on by a company that was starting to develop the first computerized stats system,” Levin said in a recent interview at Roland Garros.
He is now the director of sports analytics for SMT, which collects data at all four Grand Slam tournaments.
“We came up with a concept saying that every point ended in one of three ways,” Levin said. “A winner, a forced error or an unforced error, and every single stroke, every single result, fit into one of those categories.”
The theory was solid, but something got lost along the way. Winners are objective; errors could be too.
Now, the unforced error is a judgment call, with a healthy gray area.
On the opening point of his first service game against Rafael Nadal on Monday in the French Open, Maximilian Marterer got into an eight-shot rally and committed a forehand error to lose the point. It was labeled an unforced error.
Source : NYtimes
