The defending champions for both GP2 and GP3, Stoffel Vandoorne and Esteban Ocon, were both unable to defend their respective titles due to the ruling which forbids driver champions from returning to the series. Vandoorne remained as a McLaren reserve and test driver, where he stood in for the injured Fernando Alonso at the Bahrain Grand Prix, while also racing in the Super Formula series in Japan. Ocon served as a Mercedes development driver and was also the reserve driver for the Renault Formula 1 team, dovetailing his F1 commitments with a season in the DTM.