The Biggest Obstacles Serena Williams Faces in Quest for Calendar Slam

Serena Williams overcame potential stumbling blocks in each of her Grand Slam title runs this season. A month from now, at the U.S. Open, Williams must clear a few more hurdles in the final leg of her quest for a calendar Grand Slam.  

It won't be easy. As she told the Guardian, after winning Wimbledon, "Like I always say, there's 127 other people that don't want to see me win. Nothing personal, they just want to win...I had a really tough draw (at Wimbledon). This gives me confidence that if I had this draw, I can do it again."

At the Australian Open, Williams battled a persistent cough. She also withstood a tough match against Garbine Muguruza.

The French Open saw her in a testy fourth-round three-setter against Azarenka. Williams also played through flu-like symptoms.

Wimbledon produced perhaps her toughest test. She trailed Heather Watson 0-3 in the third set before staging a comeback. She had to defeat sister Venus in the fourth round and then a motivated Azarenka in the quarterfinals. After dismissing Maria Sharapova in the semifinals, Williams fought off hard-hitting Muguruza in the final.  

She completed her second "Serena Slam," holding all four titles at once, with her win at Wimbledon. Now Williams tries to achieve the calendar Slam, something only five tennis players, in the history of the sport, have been able to do.  

What are the biggest obstacles standing in her way?

5. Elbow Injury

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Serena Williams hits a backhand at the 2015 Swedish Open.

Williams withdrew from the Swedish Open before her second-round match due to a right elbow injury she suffered in practice. The move was reportedly precautionary to avoid a more serious injury.

If the elbow injury was brought on by overuse, some rest and relaxation should be sufficient for Williams. However, if there is a deeper issue, the right elbow could cause problems with her serve—her best weapon.

Williams also withdrew from Rome with a right elbow issue, with the French Open just days away. 

4. Rising Stars

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Garbine Muguruza shows off the runner-up trophy at the 2015 Wimbledon championships.

The WTA Tour often identifies young players with potential and calls them rising stars. The older Williams gets, the more past, present and future rising stars she stands to face.

The most notable rising stars include Muguruza, Madison Keys, Belinda Bencic and Eugenie Bouchard. But there are some others who have gained momentum recently.

This includes Anna Karolina Schmiedlova, 20, who has won two WTA titles this year. She began the year ranked in the low 70s. She reached a career-high No. 41 in June. She's ranked No. 43 and No. 26 in the Road to Singapore, based on points earned this year. She's won eight of her last nine matches. 

A young, up-and-coming player like that, in the first week, would relish a chance to knock off Williams. 

Remember, Williams was once a rising star. The 21-Slam winner is most vulnerable against those she's never played. That includes Schmiedlova.

3. Physical Fatigue

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Serena Williams during the 2015 Wimbledon ladies final.

Unlike a specific injury that might impact aspects of a player's game, physical fatigue can be like a dark cloud overshadowing everything. 

Often an accumulative effect, physical fatigue can surface at any moment and manifest itself in the inability to get dialed in.  

How Williams handles her schedule in lead-up tournaments could determine if fatigue is a factor. In 2012, she won Wimbledon, flew home to play at Stanford and then flew back to London to win Olympic gold medals in singles and doubles before returning home to win the U.S. Open.

But she's three years older. Striking a balance between remaining match-ready and rested is crucial.

2. Mental Fatigue

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Serena Williams during the 2015 Wimbledon final.

Williams has mastered the art of staying motivated. It helps to have all-time records within reach. However, with so much media attention, having to answer questions about what ifs and legacy, all the time, could wear her out mentally. 

Christ Evert told ESPNW, per Merlissa Isaacson, that mental preparation was more difficult for her as she aged. "For (Serena and Venus), it's almost 20 years, and after 15, 20 years, when I was like 32, that's when I decided, 'OK, one of every four matches, I'm not motivated.' That was the first thing to go."

1. Grand Slam Pressure

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Serena Williams waves to crowd after winning the 2015 Wimbledon final.

Going into the Wimbledon final, Williams talked of not feeling pressure. However, she opened her first game with three double faults. Before long she was down 0-2. 

Williams likes to cite Billie Jean King's quote, "Pressure is a privilege." Well, Williams must be feeling quite privileged these days. 

Just prior to Wimbledon, Williams spoke with the Associated Press about the mounting pressure to win a calendar Slam. "I've been saying that, but I really don't feel that pressure. Maybe if I would happen to win here, then maybe I might start feeling it after that."

You can bet she's feeling it. The weight of history, Steffi Graf's 22, the home crowd, the opponent, the Grand Slam winning streak...it's all-together heavy. 

The clear favorite to win at the U.S. Open, Williams must overcome an injury, rising stars and possibly mental and physical fatigue.

If she can handle the pressure, she'll enjoy a jubilant fall, having secured the No. 1 ranking for 2015. She can then arrive at the 2016 Australian Open under pressure to break Graf's record.