Americans Frances Tiafoe and Sloane Stephens began Day 1 at Wimbledon with upsets Monday. Tiafoe upstaged men’s No. 4 Stefanos Tsitsipas, and Stephens ousted women’s No. 10 Petra Kvitova.

Tiafoe earned the first upset of the day with a straight-sets win over Tsitsipas in 2 hours, 2 minutes. Tiafoe has never advanced past the quarterfinal of a Grand Slam; he next faces Spaniard Roberto Carballes Baena or Canadian Vasek Pospisil in the second round. World No. 1 Novak Djokovic and Czech Jiri Vesely were among the other men’s players to advance through early first-round matches Monday.

Stephens, holds one Grand Slam title, defeated Kvitova in just 77 minutes. The 73rd-ranked American beat the Czech 6-3, 6-4. Kvitova is a two-time Wimbledon champion. No. 6 Sofia Kenin, Madison Keys, Danielle Collins and Lauren Davis were among the other American women to advance early Monday.

The final slate of openers air from 6 to 11:30 a.m. EDT Tuesday on ESPN and from 11:30 a.m. to 4:30 p.m. EDT Tuesday on ESPN2. The women’s singles final is set for July 10, and the men’s final will be held on July 11.