Strangely, although Blaine uses Fire-type Pokémon, Rhydon isn't a Fire-type but it is a Ground/Rock type.
Blaine sent out Rhydon to fight against Ash's Charizard. Unfortunately, Charizard, still refusing to obey Ash forfeited the round, giving Blaine the win. In an attempt to make a comeback, Ash dispatched Pikachu to fight Rhydon instead. Blaine was impressed by Pikachu's speed but the electricity didn't seem to affect Rhydon.
Luckily, though, Pikachu managed to get the better of Rhydon by shocking its horn which beat it although Rhydon, as a Ground/Rock type is immune to any Electric-type attacks.