The phrase "keep the ball rolling" means to maintain momentum or progress in a situation or activity. Some possible antonyms for this phrase include "halt the progress," "stagnate the situation," "stop the flow," or "bring things to a standstill." These antonyms suggest a lack of movement or progress, a cessation of activity, or the disruption of the status quo. In some situations, it may be necessary or desirable to slow down, pause, or even stop certain activities or initiatives, but in general, keeping the ball rolling is a valuable approach to achieving success, especially in dynamic and competitive environments.