Australian Davis Cup captain Lleyton Hewitt claims he has been threatened "physically" and "blackmailed" by his former team-mate Bernard Tomic.
Hewitt, 37, said he and "close knit family" had received threats directly from the world number 88 over the past "year and a half".
Hewitt, a two-time Grand Slam singles champion, said he did not take them seriously.
Tomic could not be contacted by BBC Sport for a response.
Former world number one Hewitt was responding to comments made by Tomic after the 26-year-old's Australian Open first-round loss in Melbourne on Monday.
Tomic claimed there was a "conflict of interests" in Hewitt's Davis Cup team selections and demanded he was removed from the role.