Diego Schwartzman eased to a straight-sets win over home hope Oscar Otte but there was a shock in store for Denis Shapovalov at the Cologne Championships.
Second seed Schwartzman, ranked ninth in the world, needed just 81 minutes to seal a 6-3 6-2 victory, setting up a third-round meeting with Alejandro Davidovich Fokina.
It was a less happy outing for third seed Shapovalov in Germany, the Canadian succumbing to a 6-1 4-6 6-2 loss against Gilles Simon.
The result represented a measure of revenge for Simon after the Frenchman lost to world number 12 Shapovalov in the first round of the French Open.
He's still got it! @GillesSimon84 beats Shapovalov 6-1, 4-6, 6-2 and has scored at least one win over a Top 15 player each year since 2006.@bett1hulks | #bett1hulkschampionship pic.twitter.com/xELrNTMqmx— ATP Tour (@atptour) October 22, 2020
"I am really happy with the way I played, with the focus I had over all of the match," Simon said in his on-court interview.
"I am really happy to beat him, because it is a very, very good win. I had a tough match with him at Roland Garros. I lost it unfortunately, so I am happy that I am the winner this time."
Jannik Sinner awaits for Simon after he defeated Pierre-Hugues Herbert, while Yoshihito Nishioka also made it through.
At the European Open in Antwerp, top seed and home favourite David Goffin suffered a stunning 6-3 7-5 defeat to American qualifier Marcos Giron.
Giron's surprise victory put him in the last eight of a ATP Tour event for the first time and he saved 10 of 13 break points he faced for a maiden victory over a top-20 opponent.
Milos Raonic was not to be denied a place in the quarter-finals, though, and a 7-5 7-6 (7-4) defeat of Cameron Norrie means he will now meet Grigor Dimitrov.