Rainer grew up in Germany and played collegiate basketball in the US before eventually attending the University of Tennessee, where he earned his Ph.D. in Kinesiology with a Specialization in Sport Psychology and Motor Learning in 2011. Two years later, he founded Courtex Performance. Since then, Rainer has secured contracts with six NBA organizations as well as numerous FIBA clubs, and worked as a mental performance coach with 25+ NBA athletes, top EuroLeague players, and some of the best basketball coaches and executives in the world. Additionally, Rainer serves as the Director of Mental Performance for Canada Basketball and aims to help the Senior Men's National Team qualify for the 2027 World Cup and the 2028 Olympics. Rainer believes in proactive mental game, leadership, and culture development, and frequently helps clients navigate complex ecosystems, finetune identity and career development, and build skills and strategies to maximize performance. He resides in Charlotte, NC.