The fairytale story of the Serena Williams-Caroline Wozniacki friendship has hit a speed bump, courtesy of an old Williams "nemesis," Maria Sharapova.

USA TODAY Sports' For the Win reported that Williams made good on her promise of buying BFF Wozniacki drinks after Williams' 6-3, 6-3 victory over Wozniacki in the U.S. Open Tennis women's finals on Sunday.

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Williams posted photos of the two together on her Instagram account, with one photo including Jonas Brother Jon Jonas.

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To the U.S. Open finalists' credit, those photos were devoid of alcoholic beverages and were tame, unlike the summer-long social media photos of Cleveland Browns rookie quarterback Johnny Manziel.

However, 15 minutes after the Williams-Wozniacki selfie was posted on social media, Sharapova tweeted out a more reserved photo of herself. For the Win speculated that the photo was an intentional dig at the flamboyant Williams.

The feud between Williams and Sharapova has taken place largely way from the tennis courts. The two engaged in a war of words about each other's love lives in the summer of 2013 but seemed to have called a truce late in the year.

On the court, a rivalry really doesn't exist between the two. Williams holds a 16-2 career record over Sharapova, including 15 straight wins over the span of nearly 10 years, starting with the 2005 Australian Open.

In fact, it was Wozniacki who dispatched of Sharapova, the defending French Open champion, in a two-hour, 37-minute fourth-round match, 6-4, 2-6, 6-2. The victory marked the return of Wozniacki as a viable contender to Serena's throne.

It could be that Sharapova and Wozniacki become rivals because of Williams' stature above everyone else in women's tennis.

But it is interesting to note Sharapova's tweaking tweet as a sign that she's ready to compete with one, of not both best friends, in 2015.

Do you think Maria Sharapova can finally break through against Serena Williams in 2015? Comment below or tell us @SportsWN.