"Sometimes, on those slow serves, I just couldn't," said Venus Williams, who blasted many of those puffy serves long.
Another forehand winner off a 96mph second serve saw the Australian struggling at 15-40, "I decided to give him a really slow serve at this point," said Rafter.
She stood menacingly several steps inside the baseline on Errani's slow serves to tee off with her thunderous returns, then unleashed 125-mile-per-hour serves that froze Errani in place.
5.05pm BST Fourth set: Djokovic 6-3, 5-7, 2-6, 1-2 Nadal* 15-30, served serve, Nadal hits a slow serve with a bit of kick, Djokovic runs round it and winds up his forehand … and … slams the ball into the net.
And on the second serve, they hit a much different, more timid, perceptibly slower serve.
Her numbers were even more glaring on second serve points won, as she feasted on the slower serve to win 58 percent of the points.
Mauresmo defeated Alicia Molike, 7-5, 7-5; Zuluaga defeated Aniko Kapros, the Hungarian with one of the slowest serves on the circuit, 6-4, 6-2.
But slower serves can swerve unpredictably--by as much as a meter--and now a mathematician has explained why.
Her marginally slower serves into the body showed that Sharapova didn't have quite as clear a head as she does normally.
He also noticed Boris didn't like the slower serve to the body.
