On the verge of history, Serena Williams arrives at Arthur Ashe Stadium to face Madison Keys in the Round of 16 of the US Open. A free live stream of the contest scheduled for 3:30 p.m. local time can be found here. Additional TV coverage can be found on ESPN2.

The No. 1-seeded Williams has won all 24 Grand Slam matches she's played in this year. She's four shy of completing tennis' first true Grand Slam since Steffi Graff in 1988.

The pressure is mounting, but Williams is cognizant enough to acknowledge it.

"I mean, of course it's there. I'm not a robot or anything," the 33-year-old said, per the Boston Herald. "But at the end of the day I'm just here to do the best I can. If that means I win, then great. But if it doesn't, then you know what? I can't let that affect me."

Standing in her way, Keys is more than willing to accept her role as villain.

"What am I going to say? 'I want her to beat me?'" she asked. "I mean, yeah, I want to go out and I want to win. I mean, obviously it's a big story: She's won four [major titles] in a row and she's going for the calendar-year [Grand Slam]. That's great, but at the same time I want to win.

"So I'd be OK with beating her, yeah."

It won't come easy. The two only previously met in the semifinals of the 2015 Australian Open. Williams emerged victorious, 7-6(5), 6-2.

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