Belinda Bencic went a set down to world number 88 Misaki Doi before recovering to progress to the third round at the US Open on Wednesday evening.
The 18-year-old hit six aces on her way to defeating Doi 5-7 7-6(3) 6-3.
Swiss number one Bencic struggled to control the match early on though, as the Japanese player broke to take the first set.
Doi kept up the pressure in the second, but Bencic held her nerve to take the tie-break 7-3.
The youngster finally found her full range in the final set, breaking 24-year-old Doi twice before claiming the victory.
