The 17-year-old was playing in her first grand slam quarterfinal, but trailing 4-0 in the second set, a frustrated Gauff smashed her racquet on the clay court after she double faulted.
Gauff ran her opponent close in the opening set, with Krejcikova needing a dramatic tiebreak to gain the upper hand in the match.
In the second set, the Czech player ramped up the pressure on her younger opponent, winning the first five games without reply.
But the American showed experience to belie her age, saving multiple match points and winning three straight games to make things nervy before Krejcikova claimed the second set’s decisive ninth game to reach the semifinals.
“Already for me this is something I have never dreamed of. I was really playing a great match and Coco is incredible — she is 17, it’s amazing.”
Both players were playing in their first career singles grand slam quarterfinals. By reaching the last eight, Gauff had become the youngest woman to compete in a grand slam quarterfinal since 2006.
Despite her age, the 17-year-old Gauff didn’t look out of place on the big stage on Court Philippe Chatrier.
The No. 24 seed held 3-0 and 5-3 leads in the opening set, but Krejcikova fought back, saving five match points before eventually taking the 72-minute set.
That really seemed to kick the world No. 33 into gear.
She looked much more comfortable in the second set, manipulating the ball at will, with Gauff struggling to gain any momentum.
And leading 5-0 in the second set and needing just one more game to reach her first singles grand slam semifinal, that looked like a formality for Krejcikova with Gauff appearing rattled.
However, Gauff showed remarkable strength and resilience to save multiple match points to win three straight games and suggest a previously unthinkable recovery might just be possible.
But it was not to be and on Krejcikova’s sixth match point the Czech player clinched the match after one hour and 50 minutes.
Krejcikova will face defending champion Iga Swiatek or Greece’s Maria Sakkari for a place in the final at Roland Garros.