Madison Keys fought back from a set and 4-1 down to end Mirra Andreeva's hopes of becoming the youngest Wimbledon quarter-finalist in 26 years on Monday.
The 18th-ranked American came through against the 16-year-old Russian 3-6, 7-6 (7/4), 6-2 to make the last eight for the first time since 2015.
However, the tie ended in controversy when Andreeva was handed her second code violation of the match for slamming her racquet into the ground at deuce in the eighth game of the final set.
She was hit with a penalty point which in turn gave Keys match point, with the American going on to seal the tie.
Andreeva protested that she had slipped and had not banged her racquet into the surface intentionally.
"I knew she's a phenomenal player. I knew I had to stay in the match and get an opportunity to break back. I got the momentum and kept going," said Keys, whose big game yielded 39 winners and 40 unforced errors.
"I'd be lying if I said I wasn't feeling the pressure (of facing a qualifier). I didn't want to be the first player to lose to her to get to her first quarter-final at a Slam."
For the second major in succession, Andreeva had come through qualifying to make the main draw and was hoping to become the youngest quarter-finalist at Wimbledon since compatriot Anna Kournikova in 1997.
She was comfortably on course in the early stages out on Court 2.
Andreeva, playing in only her second Grand Slam tournament compared to the 41 of Keys, broke the 28-year-old American three times in the opening set.
The teenager remained in control in the second set, breaking in the second game and stretching out to a 3-0 lead.
Keys dug deep to fight off break points in the fourth and sixth games and pounced on a rare, loose service game by the Russian to recover the break in the seventh game.
The American swept through the tiebreaker and a frustrated Andreeva was hit with her first code violation for petulantly throwing her racquet at her chair.
Andreeva double-faulted as she slipped 2-0 down in the decider before the composed Keys ran away with a tie in which she saved eight of 12 break points.
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