Ensures chromosome alignment and accurate chromosome segregation during mitosis. Promotes proper kinetochore- microtubule (k-MT) interactions during anaphase B. The phosphorylation status of nsk1 affects the proper k-MT coupling; ensuring that it interacts stably only at the correct time during mitosis. {ECO:0000269|PubMed:21965289; ECO:0000269|PubMed:22065639}.