The phrase "come into play" means to become relevant or significant in a given situation. It is a commonly used expression and has several synonyms that can be used in its place. Some of these alternative phrases are "enter the picture," "take effect," "be activated," "come into effect," "kick in," and "get involved." These synonyms can be used interchangeably depending on the context of the sentence. For instance, instead of saying "When the team gets tired, their substitutes come into play," one might say, "When the team gets tired, their replacements enter the picture." Overall, using synonyms for the phrase "come into play" can help add variation and depth to one's writing or speech.