Olympic champion Alexander Zverev led the German tennis men into the group phase of the Davis Cup, but he wasn't really happy about it at first.

After beating Brazilian Thiago Monteiro 6-1, 7-5 in the top singles, the 24-year-old quickly disappeared from Center Court in Rio de Janeiro's Olympic Park on Saturday evening.

"We were booed here the whole time, at some point it was enough," Zverev justified his lack of celebration on the pitch.

The 24-year-old was particularly angry that he repeatedly felt insulted by part of the audience.

"The spectators have crossed a line," said Zverev.

"You can hate me, dislike me.

But if it goes against your family or against someone you love, then a line is crossed," said Zverev.

"And that was exceeded in almost every single game here today."

Allusions to Acapulco

A week and a half after his freak out at the ATP tournament in Acapulco, events in Mexico caught up with him again.

"This is Acapulco," some fans shouted in reference to his disqualification last week from the middle of the second set.

In Acapulco, after losing a double, Zverev hit the referee's chair several times with a tennis racket and almost hit the referee in the foot.

Zverev was subsequently banned from the tournament and fined.

In addition, the men's organization ATP is still investigating against him.

After the events in Acapulco, Zverev decided at very short notice to make his comeback in the Davis Cup.

Probably also to polish up his battered image again.

And in terms of sport, the third in the world rankings succeeded across the board.

After his clear two-set win against Thiago Seyboth Wild on Friday, he didn't give Monteiro a chance from the start.

Zverev managed a quick break, after just 32 minutes he secured the first set.

In the second round, Monteiro put up more resistance.

When the score was 4: 5, Zverev even had to fend off a set ball, the audience was loud again - and not always fair.

But Zverev stayed calm on the pitch and made the victory and progression perfect with the first match ball.

The fifth individual was not held after the decision.

Team boss Kohlmann is satisfied

Before Zverev's second victory, Kevin Krawietz and Tim Pütz had put the German team on the road to victory.

The German doubles won against Felipe Meligeni Rodrigues Alves and Bruno Soares 4: 6, 7: 6 (7: 4), 6: 4.

"I think that was a very decisive match," said Pütz.

The German duo improved after losing the first set and kept their nerves in the decisive phases.

“After last year's semifinals, we really wanted to get back into the group stage.

That was the minimum goal,” said team boss Michael Kohlmann with satisfaction.

The group stage will take place in September at four locations to be determined.

The German Tennis Association is also considering an application to organize a group.

The finals are currently scheduled for November.