According the Associated Press, Serena Williams entered Tuesday with a 37-0 record in the first round at Grand Slam tournaments.
She also began the day with a four-match losing streak, the longest of her career.
Williams focused on the second of those statistics, the more discouraging one.
Finally, on match point No. 9, Zakopalova pushed a forehand wide to seal Williams’ 6-3, 6-7 (5), 6-4 victory, leaving the 10-time Grand Slam champion screaming and hopping at the baseline in a mix of joy and relief.
She finished with the same number of unforced errors as winners, 35, wound up wasting 13 of 20 break points and put only 55 percent of her first serves in play.
Williams called her performance “horrendous,” and said: “I just played junior tennis — or even worse.”
Information from the Associated Press contributed to this report.