Serena Williams' sometimes puzzling decision-making is almost as fascinating as her talent. And her sister Venus very could well be the cause of that decision-making.

In an almost unnoticed development at the U.S. Open, Williams had to take an injury timeout during her doubles match Tuesday with Venus as they took on Ekatarina Marakova and Elena Vesnina to put a heavy strap on her right foot and ankle, according to Yahoo! Sports.

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The timeout took place early in the second set of the sisters' 7-6 (5), 6-4 loss to the Russians. Serena Williams, who came into the U.S. Open singles competition without having advanced past the fourth round in the three previous Grand Slams this year, kept playing with Venus.

Why Serena didn't withdraw or forfeit immediately would seem to suggest that she does not want to let down her older sister. While winning doubles events is nice, especially with her sister, Serena's in the business to win singles events and titles.

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Or at least she should be.

Serena labored through her sore foot to start her quarterfinals singles match against Flavia Pennetta and found herself trailing 3-0 in the opening set. She managed to get on track and beat Pennetta 6-2, 6-3 to advance to the semifinals.

Obviously, Serena knows her body than anyone, and she determined that she could finish her doubles match with Venus.

But why take that chance when she has her best chance of winning a Grand Slam in 2014?

The answer could be Venus, when Serena's bizarre behavior at Wimbledon is considered. The younger Williams inexplicably took to the court with Venus in July, a couple of days after losing her singles match in a third-round upset.

Serena later admitted to feeling ill before the doubles match but tried to play through it.

There, too, Serena had no business trying to play and had no rational explanation as to why she tried to play. Could it be that she didn't want to let down Venus, her doubles partner, by forfeiting before the match started?

If that is the case, then Venus needs to have a serious heart-to-heart with Serena and explain that Serena doesn't have to squander away chances of winning Grand Slam singles titles by competing in doubles with her sister.

Do you think Serena Williams is trying to please Venus by participating with her in doubles matches? Comment below or tell us @SportsWN.