UFC is seeking a new, short-notice opponent for Tate, sources said, but it's unclear if she will compete on the card.
ESPN has Murphy ranked No. 4 in the world at flyweight. Tate, a former UFC women's bantamweight champion and one of the biggest women's stars in promotion history, would have been making her flyweight debut.
Tate (19-8) returned from retirement last July, beating Marion Reneau by third-round TKO. The Las Vegas resident fell to Ketlen Vieira via unanimous decision in a women's bantamweight contender bout in November. Tate, 35, held the UFC women's bantamweight title in 2016 and retired later that year after a pair of losses.
Murphy (15-5) fought for the UFC women's flyweight title in her latest bout, a fourth-round TKO loss to champion Valentina Shevchenko at UFC 266 in September that snapped her five-fight winning streak. Murphy, 38, is 6-2 since moving down to flyweight from bantamweight in 2017.
UFC 276 is headlined by a middleweight title fight between champion Israel Adesanya and challenger Jared Cannonier. In the co-main event, Alexander Volkanovski will defend his featherweight belt against former champion Max Holloway in the third fight between the two.