(CNN) -- It wasn't often Boris Becker was caught out by a barrage of volleys on the court -- but the tennis great says he was stunned by the level of criticism he received after being appointed as Novak Djokovic's coach.
Eyebrows were raised when Becker, a six-time grand slam winner, swapped his seat in the television commentary box to take up a role with the Serbian star in December 2013.
Becker, who won 64 ATP titles and three Wimbledon crowns during a stellar 15-year career, is one of the most popular faces in the sport.
But he says the level of negative attention the move attracted from both inside and outside of the game was "all part of being Boris Becker."
"It was a little bit strange and I was a little bit surprised," the German told CNN's Open Court ahead of the U.S. Open starting on Monday.
"I wasn't aware I had that many doubters. I must have stepped on many toes in my life for all of them to beat the bushes and raise their opinion.
"We live in a free world and everyone is entitled to their own opinion, but I was a little bit surprised."
Becker, who ended his playing days in 1999, had never coached a top player on tour before joining forces with Djokovic.
"I like to think that I'm very comfortable within the tennis community so I was surprised by some of the doubters, but this is sometimes a part of being Boris Becker," the 46-year-old said.
"You're in the front row of life and in the headlines all the time, so a lot of people feel they're entitled to their opinion, even though they don't know anything about me."
Becker took on the challenge of restoring Djokovic to the top of the game, having lost his edge in the big matches.
He had started 2013 in confident mood by winning a third consecutive Australian Open, but the rest of the year was disappointing, losing to Rafael Nadal in the semis of the French Open and the final of the U.S. Open either side of defeat in the Wimbledon final against Andy Murray.
Becker was introduced to the Djokovic camp ahead of the 2014 Australian Open but could only watch from the sidelines as his man relinquished his grip on the title at Melbourne Park, losing to eventual champion Stan Wawrinka 9-7 in the fifth set of their quarterfinal clash.
That setback brought about fresh criticism of Djokovic's relationship with Becker -- though the German says that defeat provided the springboard which culminated in the 27-year-old winning his second Wimbledon title in July and reclaiming the No. 1 ranking.
A five-set victory over Roger Federer gave Djokovic a seventh grand slam and went a long way to vindicating Becker's decision.
"I think it made our relationship stronger," said Becker of January's Australian Open defeat, after which Djokovic reached the final at Roland Garros but again lost to Nadal.
"It made us realize that the only way out was up. The only way to quiet everybody down was to start winning again and that's what he did.
"If you coach a player like Djokovic, you expect perfection.
"You expect the best. Obviously, the locker room was full of skepticism and critics who don't want this relationship to work, so we had to move up a gear.
"Fortunately, after his Wimbledon triumph, the discussion was ended."
Djokovic and world No. 3 Federer will be the top two seeds in New York, with second-ranked Nadal having withdrawn due to wrist problems.
Djokovic has reached the final at Flushing Meadow four years in a row, but his only victory was in 2011.
Federer, meanwhile, will be seeking to extend his record of 17 grand slam titles -- but he has not triumphed in the U.S. since the fifth of his consecutive wins in 2008.