 Gaines would have his first coaching experience in the NBA with the Phoenix Suns as a player development coach, starting back in the 2010-11 season.In January 2013, Gaines was temporarily promoted to being an assistant head coach for the Phoenix Suns alongside Dan Panaggio after both Dan Majerle and Elston Turner would resign from their roles after the announcement of Lindsey Hunter being the team's interim head coach.He would then continue working under the organization throughout the rest of the 2012-13 NBA season until the Suns hired permanent replacement assistant head coaches to replace their old coaching staff, although Gaines would still work for the organization as a player development coach alongside Irving Roland during the 2013-14 and 2014-15 seasons.