Scottsdale Scorpions
After batting .319 with a .407 OBP (and leading his team in hits, home runs, RBIs, and walks) in the Nationals' fall instructional league, Harper was selected to participate in the Arizona Fall League (AFL) as a member of the Scottsdale Scorpions taxi-squad, the second-youngest player in the history of the league (two days older than when Mets' prospect Fernando Martínez appeared in the league in 2006). He batted .343 and slugged .729. On November 20, Harper and the Scottsdale Scorpions won the 2010 AFL Championship.