Alexander Zverev became the first man to reach 50 wins on the ATP Tour this season by beating Robin Haase 6-4, 7-5 Wednesday in the first round of the Swiss Indoors.

The second-seeded German moved to 50-16 in a season that has brought three titles, including the Madrid Masters.

Zverev converted all four of his break points while saving eight of the 10 held by the 47th-ranked Dutchman.

Haase used a between-the-legs lob to force a break in the second set that Zverev retrieved with his own 'tweener into the net.

Fourth-seeded Stefanos Tsitsipas reached the 40-win mark in beating Jeremy Chardy 6-2, 7-6 (3).

Jack Sock, the fifth-seeded American, was eliminated by Ernests Gulbis, 7-5, 6-4. Gulbis also beat Sock in Stockholm last week.