The year's last Grand Slam tennis tournament gets started with quite a matchup: Serena Williams and Maria Sharapova are scheduled to face each other at the U.S. Open for the first time.

The two stars meet in Arthur Ashe Stadium on Monday night.

Williams has won 23 Grand Slam singles titles, Sharapova five. Both own a career Grand Slam. Both have been ranked No. 1.

As defending champion and top seed Naomi Osaka put it: "Of course I'm going to watch it. I know you all are going to watch it. I think everyone in New York is going to watch it."

And not just in New York.

Other past U.S. Open champions in action on Day 1 include defending champion Novak Djokovic, Roger Federer and Williams' older sister, Venus.