Djokovic, who faces Finland’s Jarkko Nieminen in the second round, came under fire after his coach Boris Becker suggested they had secret signals to communicate with each other during matches.
ATP rules state players are not allowed to receive “communications of any kind, audible or visible” during a tournament match and Djokovic was visibly annoyed when the issue was raised again in his post-match press conference.
“I don’t understand what you really want,” said Djokovic, who won 6-4 6-4 6-4 on Centre Court.
“Do you want to say I’m cheating, my team? I’m really trying to figure out what’s behind this.
“I mean, are you asking only me or are you asking other players as well?
“I don’t understand what I can say, what I haven’t said already before. I’m going to repeat myself.
“I’m going to say that there are certain ways of communication which is encouragement, which is support, which is understanding the moment when to clap or say something that can lift my energy up, that can kind of motivate me to play a certain point. But it’s all within the rules.”
Djokovic added: “Of course, I accept the fact if my coach, Boris or Marian, do something that is against the rules, I have no complaint about the code violation that I get for coaching.”
Djokovic was grateful for support from a more unusual source after a sparrow flew onto the court and watched most of the match from one of the tram-lines.
Both players tried to waft the bird to safety, but they were unable to dislodge the emboldened creature, which caused much amusement to the Wimbledon crowd.
“From where I come from, from the capital of Serbia, Belgrade, there’s a special sparrow bird – I believe this bird came all the way from Belgrade to help me,” Djokovic said.
“But I was feeling for its safety, honestly, a few times. I couldn’t not notice it. I mean it just loves tennis, I guess.
“At one point Kohlschreiber was serving at the advantage side, between the first and second serve, and the bird landed literally very close to the sideline.
“She stayed there until I won that point. So I said, ‘Be my guest, stay around, if you want’.
“It was funny to see that. We had birds, mostly birds and different animals come in and out from the court, but the sparrow bird from Belgrade really stayed for the entire match.”
It was Djokovic’s first competitive match since his shock defeat to Stan Wawrinka in the French Open final three weeks ago and, while the Serbian made an unusual number of unforced errors early on, he insisted he felt sharp after his extended break.
“Did I feel any rust? Not much,” Djokovic said. “Honestly, I thought I started the match really well, breaking Philipp, losing the serve right away.
“All three sets were decided in the 10th game. After I broke him to win the first set and the second set, it was the same situation.
“I felt like in the third, as well, that’s where maybe I can have a mental edge over him. He missed a couple of shots.
“I thought my return was exceptionally good from my side, serving efficiently – just overall a great performance against a quality opponent.”
Hoping to play Djokovic in the second round was Lleyton Hewitt, but the Australian’s final appearance at SW19 ended in a marathon five-set defeat as Nieminen won 3-6 6-3 4-6 6-0 11-9.
Hewitt has announced his decision to retire after the Australian Open next year and the 2002 Wimbledon champion put in a typically gutsy display, saving three match points before his resistance finally gave way after four hours.
“I don’t get the same feeling walking into any other grounds in the world, no other tennis court, no other complex, than I do here.
“I do get goosebumps walking into this place.
“I’m so fortunate. One of the greatest things about winning this Championship is becoming a member of it.
“For me to be able to go in the member’s locker room four weeks before Wimbledon, in there with some of the older members, sit down and have a cup of tea and a chat, it’s a lot of fun.
“That’s something I can always come back and enjoy over the years.”
Fourth seed Wawrinka, fresh from his success at the French Open, is also through after he beat Portugal’s Joao Sousa in straight sets. “I know I’m playing well, I have a lot of confidence,” Wawrinka said.
“I’m confident with myself, but I’m really careful with how mentally I get ready for every match.
“So far I’m really happy with the first one. In general I feel good. I know where my game is. I feel ready for the next one.”
Fifth seed Kei Nishikori needed five sets to beat Italy’s Simone Bolelli and there were also wins for Croatia’s Marin Cilic, Bulgaria’s Grigor Dimitrov and Canadian Milos Raonic.