Early in his fourth-round match against Dominic Thiem at the United States Open on Monday, it looked as though Juan Martín del Potro should have been in quarantine instead of on a tennis court.

Instead, he put himself in the quarterfinals.

Del Potro, who had been battling an illness the past couple of days and began the match looking pallid and clammy, rallied his health and his game, beating the sixth-seeded Thiem, 1-6, 2-6, 6-1, 7-6 (1), 6-4.

After losing the first five games of the first set, the 24th-seeded del Potro called the doctor onto the court. The D.J. on Grandstand court tried to lighten the dour scene by playing Michael Jackson’s “Don’t Stop ’Til You Get Enough.”

“Fever, temperature’s risin’ now,” the song blared, knowingly, as the doctor offered del Potro two acetaminophen pills.