Hawaii Winter Baseball
In 2006, Mayberry was promoted to the A-level Clinton LumberKings of the Midwest League. On August 27 he was named Midwest League Player of the Week, and that month he was named Rangers Minor League Player of the Month. He batted .268 and hit 21 home runs (3rd in the league) with 77 RBIs (7th in the league), while scoring 77 runs (7th in the league), as his .479 slugging percentage was 7th in the league and he hit four triples and stole nine bases. He was rated by "Baseball America" as the Best Power Hitter, Best Athlete, and Best Outfield Arm among all Texas Rangers minor leaguers. He played for the West Oahu CaneFires of the Hawaii Winter Baseball league (HWB), on November 5 was named HWB Player of the Week, for the season batted .318 and led the league in slugging percentage (.545) and was second in doubles (9) and RBIs (23), and was named an HWB post-season All Star.