Vitali Schulz arranged a tryout between Dieck and Katharina Müller. They teamed up in April 2014, coached by Schulz und James Young in Dortmund. Assigned to two 2014–15 ISU Junior Grand Prix events, they placed 8th in Ljubljana, Slovenia, and 7th in Aichi, Japan. After winning the 2015 German junior national title, they were sent to the 2015 World Junior Championships in Tallinn, Estonia; ranked 13th in the short dance, they qualified for the final segment and finished 12th overall.