MELBOURNE, Australia — After bowing out of the Australian Open this week, Jack Sock and his childhood friend and doubles partner, Jackson Withrow, ended up on opposite sides of a great divide.

Withrow’s childhood dream was to play professional tennis; doubles proved to be his only portal.

Sock, the world’s second-ranked doubles player, has an Olympic gold medal from 2016 that he won in the mixed event, which led to his being honored at a University of Nebraska football game and throwing a ceremonial first pitch at a Kansas City Royals baseball game.

In addition, he shares four Grand Slam titles, three in doubles and the other in mixed.

Sock, 26, has also climbed as high as No. 8 in singles, which is where he stood last year at this time. His ranking since has tumbled to 105, but singles remains No. 1 in his heart.

“I can personally say if I’m not relevant in the singles world and my only choice is to play doubles, I’d probably stop playing tennis,” Sock said.