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Fonseca, who also reached the last eight at the Monte-Carlo Masters last week before losing to Alexander Zverev, earned a 6-3 6-2 victory over Rinderknech.

The talented Brazilian traded blows with his opponent early in the first set before getting the better of Rinderknech's serve in the fourth game on Munich's Centre Court.

On his way to claiming the first set, Fonseca was forced into saving four break points, and he opened the second set with a break of his own against the Rinderknech serve.

After squandering three break points in the seventh game, Fonseca eventually got the job done, sealing his progression with a blistering serve that whistled by Rinderknech.

"That was a super important key for today," Fonseca said on saving nine break points in the match.

"I was pretty focused on today's match, I knew it was going to be difficult.

"He's already a great player, and here at altitude he can play very good tennis. Serve and volley, and drop shots. He's full of weapons, so I needed to be very focused.

"He made some great returns today. At 3-2, when I was serving, that was a super important game to keep it up.

"I was 0/40, and then I made some good serves. For sure, these points were key for today."

Stefanos Tsitsipas and Fabian Marozsan completed their first-round match, which was suspended at 2-2 in the deciding set on because of bad light.

It was the world No.42 Marozsan, who had saved a match point at 5-6, 30-40 in the second set, who ultimately prevailed 3-6 7-6 (7-5) 6-4.