Serena's service woes showing up again

Four double faults.

That was how the most effective delivery in the history of women's tennis went out at Wimbledon. And not just regular double faults, either, but balls that barely got to the net or sailed across the box, sometimes even hitting the same side of the court.

Serena Williams' strange exit from the doubles competition at Wimbledon became one of the biggest stories of the tournament, with the top seed (alongside sister Venus) complaining of illness and retiring from a second-round match after just three games. Serena has not spoken to media since, and a statement released by the tournament said the official reason for her withdrawal was "viral illness".

Whatever was affecting her that day, the unusual display was clearly due to exceptional circumstances. Yet that wasn't Williams' only mysterious serving performance of the tournament. Though it wasn't quite as spectacular as her doubles troubles, a 6-1, 3-6, 4-6 loss to Alize Cornet in the third round of the singles draw also featured deliveries that were lacking their usual punch.

The five-time Wimbledon champion got in 66 percent of her first serves during the match with Cornet, comparable with her previous two rounds, but won only 68 percent of those points, which is 10-15 percent lower than in the first two rounds. And she won just 30 percent of the points on her second serves, less than half her rate in the first two rounds.

Some of that was due to Cornet's quality of play, as well as Williams' more error-prone performance. But a drop in the top seed's serving seemed to allow the lower-ranked Frenchwoman get back in the match.

Williams dominated the encounter until serving two double faults and being broken to 2-0 to start the second set, and then seemed to pull back. She started out getting in 75 percent of her first serves during the set, but began sending the ball up the center of the box to Cornet's body. That's where she went on four of the next five points she served, getting broken to 4-0.

In the third set, Williams went back to aiming for the sides of the box, but became predictable in her serving, sending most of her first serves to Cornet's forehand -- the side from which the Frenchwoman can do more damage -- and second serves to the backhand.

Perhaps most significantly, Williams' second serves were measured at an average of 83 MPH, 10 less than against Chanelle Scheepers in the second round. She had little explanation for her serving decline during the match.

"I thought my first two matches I served well," said Williams following her defeat. "Today, I don't know the percentages of my serve, but I do know I didn't hit as many aces. I think my first serve was down a little bit."

Williams hit three aces in the match, but also seven double faults.

"I worked really hard on my serve, so I don't know why it didn't happen today," she said.

Something similar happened during her 6-2, 6-2 second-round defeat to Spain's Garbine Muguruza at the French Open. Williams again seemed to pull back on her serving during the second set, getting in 74 percent of first serves but winning only 47 percent of the points, compared to 64 percent during the first set. Her second serve dropped from an average of 90 MPH to 83, and she won only 17 percent of points on her second serves.

Despite a bad back, Williams' serving performance against Ana Ivanovic in the fourth round of the Australian Open was the best during her three Grand Slam defeats this year. But the Serb was still able to step in and attack Williams' deliveries, hitting 16 return winners.

The biggest weapon in women's tennis has now been neutralized at three consecutive majors, which also affects Williams' game as a whole. Each time she has been sent out at a major this season, the other player has come in with a specific game plan and been able to impose it during the match. Muguruza jammed Williams, hitting the ball hard and up the center of the court. Cornet looked to her defeat of Williams in Dubai this season, aiming to hit the ball deep to the center, be creative and stay aggressive.

Tracy Austin, a two-time Grand Slam champion, told the BBC she saw similarities between the way Cornet and Ivanovic had played Williams.

"She wasn't able to get into a rhythm," said Austin of Williams. "Ana Ivanovic did the same thing at the Australian Open.

"Not letting her get into a rhythm ... taking the ball on the rise, going for big shots and not having rallies."

Williams usually uses big first serves and heavy second serves to prevent players from taking the initiative, but was unable to do so against Cornet, Muguruza and Ivanovic, getting broken 14 times in those three matches.

Compare that to Wimbledon two years ago, which was perhaps the best serving performance of her career -- she slammed 102 aces, won 91 percent of her service games, and topped out at 120 mph. Her biggest serve at the tournament this year was 117 mph.

To return to her dominant form of a year ago, Williams will have to start serving as she did before. Since others tend to go for their shots against her, any player having a good day can be a challenge.

"If I'm not playing, you know, a great, great match, these girls when they play me, they play as if they're on the ATP Tour, and then they play other girls completely different," Williams said. "So I just have to always, every time I step on the court, be a hundred times better."

Williams' unsightly double faults ended up receiving most of the attention at Wimbledon, but her performance in the singles also served notice that things have changed for her.