Gauff was sensational and showed zero signs that the moment or the matchup was too daunting for her. It's the sort of unusual calm and steady way she has progressed through the various levels of youth tennis, including reaching the U.S. Open junior final at 13 and winning the French Open junior title at 14.

The first set was remarkable: Gauff had 10 winners to only two unforced errors, all the while trading powerful groundstrokes at the baseline with Williams, and never facing a break point.

"The sky's the limit," Williams said. "It really is."

Gauff, who is black, idolized Williams and her younger sister, Serena, the first African American women since Althea Gibson in the 1950s to win a Grand Slam singles championship.

Serena has said Gauff reminds her of Venus.