FILE - In this Jan. 15, 2019, file photo, United States' Mitchell Krueger reaches for a backhand return to Serbia's Novak Djokovic during their first round match at the Australian Open tennis championships in Melbourne, Australia. Some professional tennis players and coaches are having a hard time financially right now because of the coronavirus pandemic. Unlike their counterparts in team sports, they do not have regular salaries.(AP Photo/Kin Cheung, File)

FILE - In this Jan. 15, 2019, file photo, Serbia's Novak Djokovic, left, is congratulated by United States' Mitchell Krueger after winning their first round match at the Australian Open tennis championships in Melbourne, Australia. Some professional tennis players and coaches are having a hard time financially right now because of the coronavirus pandemic. Unlike their counterparts in team sports, they do not have regular salaries. (AP Photo/Kin Cheung)

FILE - In this Aug. 29, 2019, file photo, Denis Kudla, of the United States, returns a shot to Dusan Lajovic, of Serbia, during the second round of the U.S. Open tennis championships in New York. Some professional tennis players and coaches are having a hard time financially right now because of the coronavirus pandemic. Unlike their counterparts in team sports, they do not have regular salaries. (AP Photo/Sarah Stier, File)

FILE - In this July 6, 2015, file photo, Denis Kudla of the United States serves to Marin Cilic of Croatia during their singles match at the All England Lawn Tennis Championships in Wimbledon, London. Some professional tennis players and coaches are having a hard time financially right now because of the coronavirus pandemic. Unlike their counterparts in team sports, they do not have regular salaries. (AP Photo/Pavel Golovkin, File)