Inactivation of the SAC kinase Mps1 through compounds like NMS-P715 or reversine allows cells to progress through mitosis faster than control cells, even when chromosomes exhibit severe segregation defects including lagging chromosomes during anaphase and micronuclei formation. This demonstrates that the SAC normally delays mitotic progression in response to improper kinetochore-spindle attachments. [@santaguida_chromosome_2017]