Phau, a qualifier and ranked 358th in the world, beat Youzhny, No. 14 in the rankings, 4-6, 7-5, 6-1. Phau finished off three breaks in each of the second and third sets. He was 3-of-9 in break-point situations in the final set.
Top-seeded Tommy Haas got by Benjamin Becker 4-6, 6-3, 6-3. Haas had his serve broken twice in the first set but saw only one break point the rest of the match. He won about three-quarters of the points after the first set.
He'll face Andrey Kuznetsov in the quarterfinals. Kuznetsov upset eighth-seeded Igor Sijsling 1-6, 6-3, 7-6 (7-5) by saving all three break points he faced in the third set.
Fourth-seeded Ivan Dodig beat Ivo Karlovic 7-6 (7-5), 6-3. Karlovic tied an ATP record with 44 aces in his first-round match. He had 12 more aces Thursday but lost the only break chance he faced while Dodig saved seven break points and didn't lose his serve.
In addition to the Haas-Kuznetsov match, Friday's quarterfinals have Kohlschreiber playing Evans while Dodig meets fifth-seeded Marin Cilic and Sela goes against Phau.