PARIS -- Serena Williams lost in the second round of the French Open on Wednesday, her earliest exit at a major tournament since falling in the first round at Roland Garros two years ago.
Williams, the defending French Open champion and a 17-time major winner, lost to Garbine Muguruza of Spain 6-2, 6-2.
The sisters would have met in the third round had they both won.
Serena struggled from the start against the 20-year-old Muguruza and finished the match with only eight winners and 29 unforced errors.
Muguruza was playing at the French Open for only the second time in her career. She lost in the second round last year, but reached the fourth round at the Australian Open in January.
Venus Williams' loss was the eighth time in her last nine major tournaments that she has failed to win more than one match.
The seven-time Grand Slam champion won the first set and was up an early break in the second. But the 19-year-old Schmiedlova responded by taking eight of nine games and won 2-6, 6-3, 6-4.
Since reaching the fourth round at Wimbledon in 2011, Williams has been eliminated in the first or second round at every Grand Slam tournament she has played except the 2013 Australian Open, where she reached the third round.
At 33 years old, Williams is far from her best. But the American has been having a solid season in 2014, winning a hard-court title in Dubai and reaching the final in Auckland.
Against Schmiedlova, the 29th-seeded Williams ended up with 47 unforced errors. Schmiedlova had only 20.
On another cool day in Paris, both Venus Williams and Schmiedlova were wearing an extra layer of clothing to keep warm.
Venus Williams won the last of her seven major titles at Wimbledon in 2008. She has never won the French Open, but lost to Serena in the 2002 final in their only meeting at Roland Garros.