Serena Williams will play Venus Williams in the US Open 2015 tournament on Tuesday as Serena meets perhaps the biggest obstacle to her claiming a first calendar Grand Slam - her own sister! The tennis is heating up in Week 2 at Flushing Meadows in New York, and this quarter final has a scheduled start time of 7 p.m. ET (midnight BST) as the sisters open up the night session. The match can be watched on TV on the ESPN network, or online through live stream via the link below.

This will be the 27th time the Williams sisters have played each other on the professional circuit, and Serena will be the big favorite to win this one tonight.

Serena has not lost a Grand Slam match since Wimbledon in 2014, and if she can win the US Open this week then she will be the first person to win a calendar Grand Slam since 1988.

Venus has looked to allay fears that she would find it hard to give her all and block her own sister from such an iconic achievement. The 35 year old said, "No-one is out to be a spoiler, but at the same time you're focused on winning your match."

However, she also hinted that she certainly knows how big today's game is for her sister and indicated that everyone would love to see Serena make history by achieving the calendar Grand Slam: "I think people love to see history being made."

Head to head, Serena has the edge between the siblings; claiming 15 wins compared to Venus' 11 wins through their 26 meetings.

Serena praised her sister ahead of the match, calling her "the best player in the tournament."

She said, "I'm playing, for me, the best player in the tournament, and that's never easy. She's beaten me so many times. I've taken a lot of losses off of her - more than anybody. She's a player who knows how to win, knows how to beat me, and knows my weaknesses better than anyone."

At the US Open, the sisters have had to share the spoils when coming up against one another, with each winning two of the four meetings. However, Serena has not lost at Flushing Meadows since the 2011 US Open Final when she lost to Sam Stosur. Venus meanwhile has made it through to the quarter finals of the US Open for the first time since 2010.

Today's big Women's quarter final at the US Open 2015 tennis tournament between Serena Williams and Venus Williams has a scheduled start time of 7 p.m. ET and can be watched on TV on the ESPN network or online through live stream by clicking here.