Roger Federer returns to action under the lights at the U.S. Open on Monday with confidence after he breezed into the fourth round following two five-set thrillers.
The third-seeded Swiss, chasing a record-extending 20th grand slam title, faces German veteran Philipp Kohlschreiber, a man he holds a perfect 11-0 career over.
Federer believes his back problems are behind him and that he can look forward after easily beating Feliciano Lopez in the third round.
"I needed to get over the fear of the back issue. Then I think the wobble I had in the second round was due to my preparation," he said.
"I think now I'm just trusting my movement better. My serve is there. My mind is there. I can finally focus on playing tennis and not so much about the past."
Opening proceedings on Arthur Ashe Stadium are world number one Karolina Pliskova and Jennifer Brady, who is one of three American women hoping to join Sloane Stephens and Venus Williams in the last eight.
Also on center court, CoCo Vandeweghe takes on Czech Lucie Safarova and Madison Keys faces fourth seed Elina Svitolina of Ukraine, pushing the heavy-hitters' contest between former champion Juan Martin del Potro and Austrian sixth seed Dominic Thiem to the Grandstand.
World number one Rafa Nadal, who is on a semi-final collision course with Federer, takes on Ukraine's Alexandr Dolgopolov in the second match at Arthur Ashe stadium.
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