"New ballgame" is a term used to indicate that a situation has fundamentally changed. It's often used when a task or challenge suddenly becomes much more difficult, complex, or unexpected. To convey the same meaning, one could use synonyms such as "new challenge," "different ballgame," "altered circumstances," or "changed playing field." Additionally, "fresh start," "new phase," "unfamiliar territory," "unpredictable situation," and "revised game plan" can be used interchangeably to indicate that the situation is no longer the same and requires a new approach. It's always essential to keep these synonyms in mind, as they can help to communicate the idea clearly and concisely.