Antonyms for the phrase "started the ball rolling" are numerous, and they can depend on the context in which the phrase is being used. Some antonyms could include "stopped the progress," "halted the momentum," "prevented the development," or "stifled the growth." Other options could be "ended the movement," "quashed the initiative," "abandoned the project," or "failed to ignite the process." In general, any word or phrase that implies putting a stop to progress or action could be an antonym for "started the ball rolling." It's essential to choose the right antonym based on the context to convey the intended meaning clearly.