The overwhelming market consensus that none will secure a calendar Grand Slam in 2026 stems from the historical scarcity of the achievement, last accomplished by a man in 1969, given the unique physical and tactical demands of transitioning between hard courts, clay, and grass across the Australian Open, French Open, Wimbledon, and US Open. Carlos Alcaraz maintains a minimal implied probability due to his proven versatility, recent major titles, and strong form on multiple surfaces, yet traders price in the substantial barriers of injury risk, schedule fatigue, and rising competition from players such as Jannik Sinner. Only an unprecedented injury-free campaign with flawless execution in every Grand Slam would realistically shift these probabilities.