PARIS: World number one Alexander Zverev's reign at the top of the rankings got off to a disappointing start on Wednesday as Italy's Lorenzo Musetti upset the German top seed 7-6(5) 6-2 in the Paris Masters round of 32.

The 29-year-old, who climbed to number one on Monday, suffered surprise defeat days after losing to Australia's Alex de Minaur in the Vienna Open semi-finals.

Musetti, a former world number five, seized the initiative by winning six of the final seven points of the opening-set tiebreak before taking command of the second set.

The 24-year-old Italian broke Zverev for a 2-1 lead and struck again to move 5-2 ahead on his way to victory.

World number 24 Musetti, a former French Open and Wimbledon semi-finalist, fired 29 winners and eight aces during the one-hour, 40-mnute contest to improve his head-to-head record against Zverev to 4-2.

"It's pretty shocking the level I was able to play in front of Sascha, who was serving really well, especially in the first set," Musetti said.

"It was really close. It could have gone both ways."

The win continued a resurgence for Musetti, who has been hampered by injuries throughout the 2026 season. His toughest setback came at the Australian Open, where he retired while leading 24-times Grand Slam champion Novak Djokovic by two sets in their quarter-final.

Musetti ended a four-year wait for a title in Lyon last month.

Zverev has enjoyed a breakthrough season, capturing his maiden Grand Slam title at the French Open before adding a second major crown at the US Open.

He has secured his place at the season-ending ATP Finals in Turin this month.