Plessinger wrapped up the 2018 Supercross 250SX West season winning the championship by only two points over Adam Cianciarulo. Racing for the Yamalube Star Racing Yamaha team he managed three wins for the 2018 season. Plessinger was the 2015 Monster Energy Rookie of the Year. He finished the 2017 SX season in third place overall. Prior to the championship his best season was in 2016 when he placed second overall in the 250SX East class. He placed eighth overall in the East West Showdown Main event.