Tennis superstar Maria Sharapova and 23-year-old Bulgarian tennis star-boyfriend, Grigor Dimitrov, were recently rumored to be having relationship problems as the couple allegedly un-followed each other on Twitter.

Sharapova is said to have been keeping herself busy with Sugarpova and Sugargoop, two of her business ventures, and has allegedly spent all of her free time before her 2014 US Open comeback on business matters, leaving Dimitrov out of the picture.

Rumors have intensified as Sharapova's social media posts of late were strictly focused on her endorsements and businesses. Dimitrov, on the other hand, did the opposite by professing his love for Sharapova during a promotional interview with Nike. During the session, Dimitrov told fans that he would love nothing more than to play with his tennis superstar girlfriend in a mixed doubles-- to which Sharapova reportedly responded by saying that she would only play with John McEnroe.

Despite consistent relationship troubles and breakup rumors, the tennis couple seemed to have opted to keep their silence on the matter. The tennis champions are currently in New York for the US Open which opened late last week.

Meanwhile, in a recent match with Alexandra Dulgheru, Sharapova was apparently looking troubled during the start of the game, frequently losing her temper and even glaring at judges, who at times, ruled in favor of Dulgheru. The tennis icon was undoubtedly in for a bad start and lost the first set, but quickly regained control and managed to end the game with a victory. Sharapova currently ranks number 5 in the world's women's division.