Serena Williams' coach Patrick Mouratoglou gets much of the credit for the star's incredible post-2012 French Open run.
However, the X-factor in Williams' quest for a fifth U.S. Open could be the presence of her parents.
Since teaming up with Mouratoglou last summer, Williams has won three Grand Slams. She is also 60-4 this season.
Two of those losses—Wimbledon and Cincinnati—happened without either of her parents present. Her parents also missed the Swedish Open and the Rogers Cup in Toronto. So she is 2-2 without her parents.
Williams turns 32 next month, so she's hardly a baby. But she is the baby girl in the family. Although she's been on tour for nearly 18 years, only recently has she competed at major tournaments without either of her parents present.
Could their presence make a big difference in whether Williams wins the U.S. Open? Could Williams' recent struggles with confidence be due to separation anxiety?
Remember, Williams has spent her entire life and career with her parents close by. She was even home schooled.
When Williams lost at Wimbledon, "Team Serena" was in her player's box. Mouratoglou was there. So was her longtime hitting partner Aleksandar Bajin, aka "Big Sascha." Her parents, however, were not.
It was the first time Williams played in a Grand Slam in which neither of her parents attended.
Serena refused to blame the loss on the absence of her parents. However, tennis commentator Pam Shriver told The New York Times that along with the dustup with Maria Sharapova, “Serena was out of her usual routine here. No Venus, no Mom; no Dad."
Tennis players are creatures of habit, and perhaps not being able to look up and see mom or dad left Williams feeling less secure.
At Wimbledon and Cincinnati, Serena was unable to do what she is famous for: close out a match.
Even in Toronto and Sweden, where she won without her parents, Williams looked unsteady.
Oracene Price was there for the French Open. Throughout her career, Williams' mother has always been the picture of peace. She seems to bring out the serene Serena.
Unlike the more vocal and controversial Richard Williams, Price appears to posses an inner peace that keeps her from overreacting when Serena struggles. Price describes herself as a deeply spiritual person. She sometimes even giggles when Serena makes silly, unforced errors.
In the documentary Venus and Serena, Serena describes her parents as "kind of yin and yang. If one pushed, the other pulled."
They are both protective. In 2003, after Serena was booed in a French Open match against Justin Henin, both spoke publicly about what they perceived as racist treatment. "They wanted a blonde and a ponytail," said Price.
It's unclear if either or both parents will make an appearance in Serena's box at this year's U.S. Open.
Their presence just might be the calm to defuse Serena's emotional storms.