Purpose: To compare the load and wellness of second-team academy football players during a first-team preseason with those of first-team players and those of their previous second-team preseason. Methods: Athletic Club’s first- (n = 10) and second-team (n = 9) players were prospectively followed during the 2019–20 first- and second-team and 2020–21 first-team preseasons. Weekly external and internal loads and average wellness z-scores (fatigue, sleep quality, muscle soreness, stress, and mood) were compared between preseasons and teams. Results: While training together during the 2020–21 preseason, second-team players performed more decelerations <−3 m/s² per week than first-team players (moderate effect size). For first-team players, there were only small differences between preseasons in external load, but session rating of perceived exertion was higher (moderate) and stress (moderate) and mood (large) z-scores were worse in 2020–21. For second-team players, more total distance (large), accelerations >3 m/s² (large), and decelerations <−3 m/s² (very large) were performed; total loading (moderate) and session rating of perceived exertion (moderate) were higher; and fatigue (very large) and stress (moderate) z-scores were worse during the 2020–21 first-team preseason compared to their previous second-team preseason. Conclusions: Players transitioning from the second team faced higher external and internal loads, fatigue, and stress during the first-team preseason compared to the previous second-team preseason. Player development and monitoring plans appear necessary to manage the transition from the academy to the first team.