The condition is "Contested Theater". Does this mean if Sparta controls, for instance, Naupactus, that Phormio will skip this strategy? Or, since the strategy is called control of naval Checkpoints should the condition actually be "Contested or Enemy-Controlled Theater?"
Brent has it right... however, I pick up Naupactus as a PS objective way down on the Athenian Strategy matrix, Offensive Naval, whose condition is "There is a Spartan controlled naval theater", if more than one randomize.
So, once lost Athens' strategy evolves, but it can and usually does come back to it late in the game.