After being taken by the Raptors with the 59th pick in the 2019 NBA Draft, Hernandez went on to make six appearances in his rookie season, averaging 2.3 points and 2.3 rebounds in 4.7 minutes per game. He appeared in another nine contests (all starts) for the Raptors 905 of the G League, averaging 13.7 points, 9.1 boards, 1.8 blocks and 1.0 steals. At the NBA level, the rookie set season highs with six points and two assists in an Aug. 12 win against the Sixers, making his first NBA three-pointer in the process. Two days later in the season finale, Aug. 14 against Denver, he put up a new personal best in rebounds with seven.