Squires, a former Cincinnati player who lost to eventual champion Viktor Hovland in the quarterfinals last year at Pebble Beach, was the last player to advance from two rounds of stroke play at Pinehurst No. 2 and No. 4. He needed four holes in a 27-for-3 playoff to claim the final spot in the 64-player field.
"It was kind of nice that I had already played a couple holes before the match," Squires said. "Granted, it was on (course No.) 4, which (is) a little different, but it was kind of nice. It was a little easier getting rhythm."
Squires went ahead 2 up with a birdie on the par-3 15th hole on the No. 2 course. Wu rallied on the 17th with a birdie to Squires' par, but Squires ended it with a birdie on the 18th while Wu bogeyed the hole.
Wu, the world's 11th-ranked amateur and a member of Stanford's NCAA championship team this season, finished 36 holes of stroke play at 3-under-par 137 to claim medalist honors.
"Obviously, anything can happen in match play," Wu said. "All 64 guys that made it to match play are incredible players. It doesn't feel as disappointing as losing a (No. 1 vs. No. 16 seed) in basketball."
UCLA's Devon Bling, who lost to Hovland in the final last year, was beaten 6 and 5 by Steven Fisk, the world's No. 12 amateur. Isaiah Salinda, a semifinalist a year ago and a teammate of Wu's at Stanford, beat Travis Vick 1 up.
Five of the world's top 10 amateurs advanced to match play and three of them won their opening matches: No. 3 Takumi Kanaya beat Matthias Schmid in 19 holes, No. 5 Akshay Bhatia topped R.J. Manke 3 and 2, and No. 9 Ricky Castillo defeated Chad Sewell 5 and 3.
No. 7 Stewart Hagestad lost to Maxwell Moldovan 3 and 2, and No. 10 Blake Windred was beaten by John Pak, 3 and 1.
Kanaya and Bhatia were the only two of the top six to advance out of stroke play. Top-ranked Cole Hammer, a Texan who reached the semifinals last year, was eliminated on the first playoff hole while No. 2 Conor Gough finished at 8 under - three strokes off the cut line.
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