Alexander Zverev's tenure as the No. 1 in men's tennis started with a 7-6 (5), 6-2 defeat to Lorenzo Musetti in the second round of the Paris Masters on Wednesday.

Zverev moved to the top ranking on Monday, capping off a fine season which saw him win the first two Grand Slam titles of his career at the French Open and the U.S. Open.

Despite playing on a fast indoor court which suited his serve and aggressive ground strokes, the imposing German looked out of sorts against Musetti. The mercurial Italian clinched victory with an ace in a one-sided contest where he had more winners (29-25) and less unforced errors (12-21) than Zverev.

Later Wednesday, 24-time Grand Slam champion Novak Djokovic faced qualifier Rinky Hijikata and seven-time major winner Carlos Alcaraz played American Alex Michelsen. Fourth-seeded Daniil Medvedev took on Ignacio Buse.

Djokovic needs to reach the semifinals to stand a chance of qualifying for the season-ending ATP Finals later this month. Only two spots remain for the Nov. 15-22 event in Turin, with only an ATP250 event remaining in Stockholm after Paris.

In other second-round play, three-time U.S. Open semifinalist Frances Tiafoe — seeded No. 7 — wasted four match points in a 6-3, 1-6, 7-6 (9) loss to Frenchman Quentin Halys.

Tiafoe's defeat qualified Arthur Fils for the ATP Finals. He is the first Frenchman to reach the event since Gael Monfils in 2016.