Long before he was a top-ranked player, Djokovic had earned the nicknames "Court Jester" and "Joker" for his impressions of fellow pros. He imitated Maria Sharapova's shrieks, Rafael Nadal tugging at the back of his shorts, John McEnroe's tantrums. They weren't always well-received.
The 46-year-old Becker, a six-time Grand Slam champion, was seated among Djokovic's supporters Sunday, red in the face and laughing as he watched the Serbian star mimic his characteristic rocking motion for serves.
Djokovic recruited Becker ahead of the Australian Open to help him try to win a fourth straight title. He took a step closer Sunday by beating childhood friend Fabio Fognini, 6-3, 6-0, 6-2. The win ushered Djokovic into his 19th straight Grand Slam quarterfinal.
After the match, Djokovic walked back onto the court for an interview with Jim Courier, one of Becker's main rivals in the 1990s, who asked him: "Back in the day when you did impressions, did you have any of Boris?"
Seated in the stands, Becker laughed and wagged his finger.
"Uh, yes. I did," Djokovic replied, to the crowd's delight. "But he hasn't seen it yet.
Djokovic then requested a ball and approached the baseline, where he began rocking his body back and forth with his ball on his racket to build momentum for his toss, which he then threw into the air, swung and intentionally missed as he stumbled forward.
"This was in your better days Boris, and today you look like this," Djokovic smiled, as he walked forward like a stooped old man with a limp. Becker recently had ankle surgery and hasn't been able to hit balls with the six-time Grand Slam winner since starting his new coaching job.
After the crowd quieted, Djokovic said he couldn't wait to return Becker's serve and added: "I've got to give him credit, he's trying. He's working every day."
Djokovic said the impersonation was not perfect: "I have to gain a few kilos and color my hair in order to do the proper Becker imitation."
Djokovic enters the quarterfinal on a 28-match winning streak, not having lost since his 2013 U.S. Open final defeat to Nadal.
In Melbourne, Djokovic and Nadal could face each other in the final, setting the stage for a rematch of their epic five-setter in the 2012 Australian decider.
Djokovic's next plays No. 8 Stanislas Wawrinka, who stretched him in the fourth round last year to five sets that lasted 5 hours and 2 minutes, the longest Grand Slam match of the season. Wawrinka also lost in five sets to Djokovic in the U.S. Open semifinals.
So far in Australia, Wawrinka had an opponent retire in the second set of the opening round, and received a walkover into the fourth round. On Sunday night, he had a 6-3, 7-6 (3), 7-6 (5) win over No. 17 Tommy Robredo.
"He's playing the tennis of his life," Djokovic said of Wawrinka. "You cannot expect a clear favorite in that match."