The Suns fired Jeff Hornacek late Sunday night after a 91-78 loss to the Dallas Mavericks. Hornacek compiled a 101-112 record in two-plus seasons coaching the Suns, who have lost 19 of 21 games.
Watson will make his head-coaching debut Tuesday night when the Suns (14-25) host the Toronto Raptors.
Watson, 36, was hired as an assistant coach under Hornacek on June 4 and was promoted on Dec. 28 after assistant coaches Jerry Sichting and Mike Longabardi were fired. Watson began coaching professionally last season with the San Antonio Spurs’ NBA Development League affiliate in Austin. The Suns also considered assistant coaches Cory Gaines and Nate Bjorkgren for the interim opening.
Watson spent 13 years in the NBA, mostly as a backup point guard.