US Open Tennis 2015 Results: Scores, Highlights, Reaction from Sunday Night

The 2015 U.S. Open is in full swing in Queens, New York, and there are numerous storylines surrounding the event. Serena Williams, who has been taking everyone else's lunch money on the tennis courts all year, is seeking her fourth consecutive U.S. Open title and would complete the calendar Grand Slam with a win.

Marin Cilic is the defending men's champion, but top-seeded Novak Djokovic is looking to retake control of the men's tennis world. Here's a look at the results from Sunday's action followed by some highlights and reactions.

Men's Singles

(9) Marin Cilic def. (27) Jeremy Chardy	6-3, 2-6, 7-6, 6-1
(18) Feliciano Lopez def. (32) Fabio Fognini	6-3, 7-6, 6-1
(19) Jo-Wilfried Tsonga def. Benoit Paire	6-4, 6-3, 6-4
(1) Novak Djokovic def. (23) Roberto Bautista Agut	6-3, 4-6, 6-4, 6-3

Women's Singles

(23) Venus Williams def. Anett Kontaveit	6-2, 6-1
(1) Serena Williams def. (19) Madison Keys	6-3, 6-3
Roberta Vinci def. (25) Eugenie Bouchard	Walkover
Kristina Mladenovic def. (13) Ekaterina Makarova	7-6, 4-6, 6-1

You can see the full list of results at ESPN.com.

Djokovic and Roberto Bautista Agut wasted no time getting competitive with this long exchange in the first set, courtesy of the U.S. Open on Twitter:

The biggest upset on the women's side came in the nightcap, when Kristina Mladenovic knocked off Ekaterina Makarova, who was the No. 13 seed. With the win, Mladenovic advanced to the U.S. Open quarterfinals for the first time in her career.

The tournament's participants weren't the only ones making highlights Sunday. Check out the snag this ball boy made, courtesy of the U.S. Open:

With their victories Sunday, Venus and Serena Williams will face each other in the next round. As ESPN noted, they have been facing each other in Grand Slams for a while now:

As Jamie Lisanti of Sports Illustrated noted, Serena holds a 15-11 record against Venus, and she leads Venus 8-5 in Grand Slams. 

"I would rather lose to Venus as opposed to anyone else. I, in general, don't like to lose," Serena said, per Lisanti. "Yeah, so hopefully we'll just go out and do the best that we can, and whatever happens hopefully have a good attitude about it.​"

Play will resume at the U.S. Open on Monday at 11 a.m. ET. Second-seeded Roger Federer will hit the court at 9 p.m to face 13th-seeded John Isner. Simona Halep, the second seed on the women's side, will take on Sabine Lisicki, the 24th seed, at 12:30 p.m.