NEW YORK, NY, USA - Qualifier Taylor Townsend stuck with her gameplan to back up her upset of Simona Halep, skipping and serve-and-volleying her way to a 7-5, 6-2 defeat of Sorana Cirstea and a Grand Slam fourth-round debut in one hour and 27 minutes.

The American becomes the first qualifier to reach the second week of the US Open since 2015, when both Johanna Konta and Anett Kontaveit reached that stage - and, after four straight matches starting from the second qualifying round in which she had to come back from a set down, managed to eke out a tight first set in which she trailed most of the way before rolling through the second. Having come to the net 105 times against Halep in the second round, Townsend added another 74 approaches today - and though the strategy felt like a tightrope walk at times, 46 won points demonstrated how her boldness paid off.

The match was a fascinating study in strategy, particularly in the context of Townsend throwing caution to the wind and committing herself to all-out net-rushing to stun the Wimbledon champion in the previous round. The 23-year-old started exactly as she had left off, serve-and-volleying with abandon and rushing the net as soon as humanly possible on the Cirstea delivery - often directly off the return.

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But where Halep had been taken by surprise, her Romanian compatriot was prepared. Cirstea repeatedly nailed down-the-line returns that left Townsend stranded, scoring five clean return winners in the first set - while successfully taking the net away from her opponent by approaching herself. Indeed, as Cirstea came through a three-break sequence to take a 3-1 lead, she was the one executing with far more clarity of purpose in the forecourt.

As she had against Halep, though, Townsend was able to adjust magnificently. The World No.116 did not abandon her strategy but began to deploy in more judiciously, opting to stay back on occasion rather than swarming the net off everything. This was key to getting back into the set: two consecutive baseline winners, both superbly angled backhands, sealed the break back for 2-3. Of course, Townsend could not be kept away from the net for long - and that also paid off as she saved three break points with a magnificent blend of touch and power to level for 3-3.

After five straight games that had featured at least one break point, both players hit a golden patch of serving to emerge tied at 5-5 - at which point, with clutch play under pressure at a premium, it was Townsend, once again rushing the net straight off the return, who took the spoils. Cirstea was unable to execute the tactics that had served her so well at the start of the match - and a succession of errors on attempted passes from the World No.106 ensured that Townsend, who had been behind for the entire set, would rattle off its final eight points to take the lead.

Townsend, sensing her opportunity to take firm control of the match, kept her feet moving between sets by producing a rope from her racquet bag and skipping while Cirstea left the court - and continued to press on resumption of play, coming up with a wonderfully controlled lob winner en route to breaking a still-rattled Cirstea. From there, she rolled. Having had her strategy hampered by a lack of first serves early on, Townsend raised her first serve percentage from 61% in the first set to 78% in the second - and consequently would not face a break point until the final game of the match.

Those, too, were dealt with in short order: Townsend produced consecutive aces, her fourth and fifth of the day, to reach match point, whereupon another unreturnable serve sealed a berth in the fourth round against either No.15 seed Bianca Andreescu or No.19 seed Caroline Wozniacki.