"Rory was very upset by it and even Serena Williams pointed out – albeit in a joking way – it was a pretty mean thing to do," the Independent cites a source saying.
The report says the pair broke up just days after the picture went up, but that Wozniacki still hasn't accepted it.
"There were a lot of tears. She still has her profile picture on her social-networking site set as the two of them in happier times, but I can tell you the pair are no longer an item," a source says.
However, according to USA Today's translation of a report in the Danish newspaper Ekstra Bladet, Wozniacki is denying there's any trouble in paradise:
“I’m so tired of the rumors. They occur every time Rory and I are apart a few days or do not write on Twitter. There is nothing in it, and from now on I just think that I will keep my private life private. It is so annoying that the media and the so-called sources constantly spread the rumors. They write just what they want.
“[...] All is well [with the relationship], and then there’s not much more to say about it. I just want to be allowed to live my life off the court without all the speculation.”