Marketa Vondrousova pulled off a huge surprise on Saturday, defeating the in-form 13th seed Kiki Bertens 7-6 (4), 2-6, 7-6 (1) to in the third round of the US Open to start the action on Louis Armstrong Stadium.
The Czech trailed by a break in both the first and third sets before rallying to dominate both tiebreaks. The 19-year old lefty will face Ukranian Lesia Tsurenko in the Round of 16 on Labor Day.
Vondrousova blows away Bertens in breaker to claim the first set
The young Czech went toe-to-toe with her more favored and experienced opponent through the first four games before Bertens made the first breakthrough of the match, breaking on her fourth chance when Vondrousova sent a forehand into the net for a 3-2 lead.
Bertens was mixing in exquisite volleys and powerful serves, blazing through her next two service games at love to lead 5-3. It was the Vondrousova forehand that kept her in contact as she held to trim the deficit to 5-4.
It was that wing that got her back to even, breaking with a pinpoint forehand to square the set at 5-5. Each player held to force a tiebreaker where the 13th seed collapsed, double-faulting on her first two service points to hand Vondrousova a 3-0 lead.
Mixing in effective net play, the teenager was handed two set points, converting on the first when she finished off the set with a beautiful forehand volley winner to take a set she looked to be all but out of.
Bertens runs away with second set after recovering from an early break deficit
It looked to be more of the same to open the second set, Vondrousova's massive forehands forcing Bertens to panic and dump a drop shot into the net on break point. A quick hold gave the Czech a 2-0 lead and a straight sets upset was looking like a strong possibility.
Suddenly, it was the Dutchwoman's powerful serve and forehand that started to find the mark, reeling off 11 consecutive points to take a 3-2 lead.
Errors were starting to creep into the Vondrousova game and she made a barrage of them to get broken for a second straight time. The Cincinnati champion was on a roll and she fired an ace for a 5-2 lead.
Ranked 103rd and the last direct entry into the tournament, the 19-year old was showing why she has slid out of the Top 50 and she was summarily broken to love, Bertens winning six games on the trot to square the match at one set all.
Vondrousova claims final set tiebreak to post the biggest win of her career
The beginning of the final set resembled the beginning of the match as five straight holds were posted to see Bertens take a 3-2 lead. The Dutchwoman took the initial break in the sixth game by firing a backhand winner down the line to move within two games of victory.
Vondrusova's forehand was back on display, using it to great effect to break back straightaway. At 5-5, the Czech overturned a 40-0 deficit to break and serve for the match, but Bertens would have an answer, ripping three straight backhand winners to stay alive and force a final set tiebreak.
After dropping the opening point, Vondrousova was the beneficiary of a pair of net cords before blasting a forehand once more for a 3-1 advantage. She never looked back and on match point, a fourth successive error gave the 19-year old a career-changing win.