Gauff downs Andreeva, 16, to make US Open third round
Sixth seed Gauff, one of the favourites for the title after recent tournament wins in Washington and Cincinnati, will meet Belgium's Elise Mertens or countrywoman Danielle Collins for a place in the last 16.
After a tough opening round against German veteran Laura Siegemund, Gauff dominated the youngest player in the draw to notch a 13th win in 14 matches since losing in the Wimbledon first round.
The 19-year-old defeated Andreeva for the second time in three Grand Slams after winning their French Open clash in the first act of a potentially era-defining rivalry.
"I just learned to be aggressive, because if you give her something she is going to take advantage," said Gauff, who was taken to three sets by Andreeva at Roland Garros in June.
"I did well today making her play off her back foot.
"She has a great future in front of her - I think she is going to be back on this stage many more times."