The Swedish table tennis pair struggled in their round-of-16 match in Ljubljana, but ultimately beat Marcos Freitas and Tiago Apolonia 11–9, 9–11, 11–8, 15–13.
The Portuguese pair had four set points in the fourth set to force a deciding set, but Karlsson and Källberg saved them all and then converted their second match point.
Tough opposition awaits in the quarterfinals: Germany’s Dang Qiu and Benedikt Duda.
Later in the morning, Truls Möregårdh and Elias Ranefur will play their round-of-16 match in the doubles tournament. This afternoon, Möregårdh and several other Swedes will also play singles.
In the women’s doubles, Stina Källberg and Filippa Bergand were eliminated, losing 1–3 to Germany’s Nina Mittelham and Annett Kaufmann.