Zverev knocked Federer out of the ATP Finals semi-finals this afternoon with a 7-5, 7-6(5) victory.
However, deep into the second set tiebreak a ball boy dropped a ball and ran a couple of meters forward to collect it.
Federer and Zverev were engaged in a baseline rally at 4-3 when the incident occurred behind the Swiss star.
World No 5 Zverev stopped play and told the umpire that the disturbance happened within his eye line.
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Federer was confused an sought clarification from the official before then confronting the ball boy.
And when asked what he said to the youngster, Federer tried to lighten the mood.
"Maybe he's coming to dinner, I don't know," he joked.
"Give me a smile, don't be too serious, please. It was a joke."
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Federer then explained how there was no bad blood between himself and the volunteer.
"I just asked him, 'Did you drop the ball?' I didn't understand what he said. I said, 'Did you drop the ball?'," Federer said.
"He said, 'Yes, I did drop the ball.'
"From that standpoint, it's, Okay, no problem, that happens.
"It's all good. It's all good. I hope he doesn't have a sleepless night. It's not a big deal at the end of the day.
"It could have been if maybe I win the next point.
"Whatever happened, this is life, this is sports. I'm definitely not mad at him. It's all good, you know, from my side."
Federer also claimed to be in the dark over rules.
"I don't know what's rules are," he said.
"I just think I was trying to think what would I have done in his position, you know. It's bold to stop the rally because I don't know if it's an umpire's decision or not.
"While you're hitting, that might go through your head. So I would have probably said, 'Whew, I'll probably keep on playing', unless the ball really rolls into the court quick.
"I don't know what happened actually. Was it a bounce and it rolled, or a bounce and he picked it up?"