By Mike McDaniel After falling short in the NBA Finals, the father of the Celtics star shared a heartwarming message for his son on Instagram. View the original article to see embedded media. After the Celtics fell to the Warriors in the NBA Finals earlier this week, Boston wing Jayson Tatum received more than his fair share of criticism for his poor performance in the championship round. Despite turning in his best season as a professional, Tatum struggled in the NBA Finals, shooting just 36.7% from the floor overall. Tatum also averaged nearly four turnovers per game, which underscored Bosto…