The 3-1 victory over home player Ricardo Walther was controlled for the most part. However, there was a bit of nervousness in the match when the German - who was treated for an injury early in the second set - won the third set and reduced the score to 1-2.
But it only proved to be a small bump on the road for Källberg.
For in the next, the 27-year-old secured a semifinal spot in Frankfurt.
It was probably harder for him to play than it was for me, says the Swede in the post-match interview on Youtube, thinking of Walther's injury.
I hope he's okay and that it doesn't hurt too much.
If the road to the semifinal was relatively easy, something else awaits in the next match on Saturday.
There, his compatriot Truls Möregårdh awaits.
The star won the star duel against Frenchman Félix Lebrun with 3-1 - which was the 22-year-old's first - and again displayed a copy of Swedish national team player Viktor Gyökeres' victory gesture.
I've had it tough against the Lebrun brothers and wanted some kind of revenge and at least win against one of them. I'm glad about this, he says in the post-match interview on Youtube.
The last time the Swedes faced each other was in the European Championship quarterfinals in Linz, when Möregårdh won with 4-2.
I hope I'm the Swede who reaches the final. We know each other very well and it's going to be a tough match for both of us, says Möregårdh.
