TENNIS : Serena's partying causes icy rift with Venus

Tennis insiders are whispering that  Serena Williams ' partying has caused an icy rift between her and her sister,  Venus Williams .

The tennis champs have not been seen together off the court in recent weeks, and many wonder if Serena's  late nights out  and disappointing doubles performances have annoyed the more low-key Venus.

An insider was heard during the US Open claiming, “They're not in a good place right now. Venus is angry with Serena,” because of her  active social life off the court .

Some noticed Venus and Serena didn't arrive together or even speak to each other at the Taste of Tennis kickoff event for the US Open a few weeks ago.

“There was no acknowledgment that either one was even there,” said one.

Nor have they been visible on one another's Instagram feeds.

The last picture of Venus on Serena's feed was three months ago; Serena appeared on Venus' feed two months ago. On Tuesday, there was no sign of Venus at Serena's presentation of her HSN clothing line at the Style360 lounge during Fashion Week.

The sisters lost in the US Open women's doubles quarterfinals after they had to  pull out at Wimbledon , where Serena developed a mysterious illness. They'd also declined to appear together at a mandatory press conference after losing at the US Open. But Serena bounced back to win the US Open singles  title on Sunday.

Venus' rep, Lisa Sorensen, told us Venus was not with Serena after the US Open because she went directly to Canada to prepare for the Quebec City WTA Open. She denied any rift: “I am very surprised by these accusations. They are completely false. Venus and Serena always have been and continue to be close and supportive of one another.”

Serena's rep, Kelly Bush Novak, also denied any bad blood between the sisters, and called our story an “absolute lie and reckless . . . They continue to be each other's biggest fans and a beacon of support for each other. There is no change in their very close and special relationship.”