Vaporeon: The player loses against the rival at both Professor Oak's lab and Route 22.
Flareon: The player wins against the rival at Professor Oak's lab, but loses the Route 22 battle (or vice versa).
Jolteon: The player wins against the rival at both Professor Oak's lab and Route 22.
In the fourth through seventh battles, Blue has one Potion per Pokémon that he uses 12.5% of the time if their HP falls below 20%.
In the Champion battle, he instead uses Full Restores with the same logic.
This battle is available until the player defeats Brock. If the player skips this battle, it is treated as a loss for the purposes of determining which Eeveelution the rival evolves his Eevee into.
This battle can be skipped by obtaining a Pokémon with Cut from a trade, and then leaving Cerulean City by cutting the tree blocking the south exit.
If this battle is skipped, it is possible to break the gameplay sequence by having this battle at any point later in the game (even after other battles against Blue).