Dominik Koepfer defeated Ivo Karlovic in the quarterfinals of the Houston Champions Cup, an ATP Challenger event played on hard court on 16 November 2018. The German's victory over the Croatian serve-and-volley specialist represented a significant scalp at the Challenger level, where Karlovic remained a formidable opponent despite his age. Koepfer's win advanced him towards the tournament's latter stages and demonstrated his growing competitiveness on the North American hard-court circuit. The result marked continued progress in Koepfer's career trajectory during the 2018 season.