This lesson explores the fundamental principle that tennis is a game of errors, with 70-83% of points ending in mistakes rather than winners. Coach Craig O’Shannessy introduces an essential framework of eight key elements to force errors: consistency, direction, depth, height, spin, power, court position, and time. He highlights the importance of depth as the "diamond" of these factors and demonstrates its role in effective shot patterns, particularly in run-around forehands. Practical drills to incorporate depth and other elements into player development are discussed, with an emphasis on improving player strategy and execution.