The thought of preparing for a semi-final with two days' rest did not enter Daniil Medvedev's mind as injury threatened his US Open hopes.
A thigh injury looked as if it might end Daniil Medvedev's US Open, but he fought through it to beat Stan Wawrinka in four sets.
For Novak Djokovic, losing ground in his pursuit of the grand slam singles titles record will sting more than his injured shoulder.
Despite having an idea he was playing a wounded Novak Djokovic, Stan Wawrinka was still surprised by his opponent's retirement in New York.
After ending his US Open defence prematurely, world number one Novak Djokovic spoke of the pain he has dealt with in his left shoulder.
Stan Wawrinka was in command against Novak Djokovic when the defending champion retired at the US Open.
World number one Novak Djokovic saw his US Open defence end as he retired in the third set against Stan Wawrinka.
On a day dominated by five-set matches, Rafael Nadal did not even have to play a game to progress at the US Open.
Despite contrasting first-round matches at the US Open, Novak Djokovic and Roger Federer advanced.
Stefanos Tsitsipas was sent packing following a shock defeat to Jan-Lennard Struff, while Alexander Zverev joined him out the door.