before his win against Evgeni Kondratov. After amassing a record of 14–2–1 during his first three years in the sport, Procházka as the first Czech entered the Rizin Fighting Federation in 2015. Rizin Fighting Federation Heavyweight Grand Prix Procházka made his promotional debut against Satoshi Ishii on December 29, 2015 in the World Grand Prix 2015 –100 kg tournament at the Rizin FF's first event Saraba no Utake. He won the quarter-final fight via knockout in the first round. Procházka's next fight in the Rizin FF's -100 kg tournament was at Iza no Mai on December 31, 2015. He won the semi-final fight against Vadim Nemkov via technical knockout. Later that same night, he lost in the final round against Muhammed Lawal via knockout in the first round. Procházka weighed in at 95.9 kgs (211.5 pounds) for the tournament. Procházka faced Kazuyuki Fujita on April 17, 2016 at Rizin 1 at a catchweight of 110 kgs (242.5 pounds). Procházka weighed in at 98.6 kgs (217.3 pounds) for the bout. He won the fight via technical knockout in the first round. Procházka faced Mark Tanios on September 25, 2016 at Rizin 2 - Rizin Fighting World Grand Prix 2016: Opening Round. He won the fight via unanimous decision. Procházka suffered a knee injury during the fight and was subsequently pulled from the tournament. Return to Light Heavyweight Procházka faced Willian Roberto Alves on September 29, 2017, at Fusion FN 16 - Cage Fight, the homecoming event organized by his team. He won the fight via technical knockout in the first round. Procházka faced Karl Albrektsson on December 29, 2017 at Rizin Fighting World Grand Prix 2017 - Bantamweight Tournament: 2nd Round. He won the fight via technical knockout in the first round. Procházka faced Bruno Cappelozza on July 28, 2018, at Rizin 11. He won the fight via knockout in the first round. Procházka faced Jake Heun on September 30, 2018 at Rizin 13. He won the fight via technical knockout in the first round. Procházka was scheduled to face Emanuel Newton on December 31, 2018 at Rizin 14. However, Newton was pulled out of the fight, citing a rib injury. Procházka remained on the card and was rescheduled to face Brandon Halsey. He won the fight via technical knockout in the first round. Inaugural Light Heavyweight Champion Procházka faced Muhammed Lawal in rematch on April 21, 2019 at Rizin 15