Background: Attentional resource allocation during sports practice is associated with the players’ perceived mental load. However, few ecological studies address this problem by considering the players’ characteristics (e.g., practice experience, skill and cognition). Therefore, this study aimed to analyse the dose-response effect of two different types of practice, each with different learning objectives, on mental load and motor performance by using a linear mixed model analysis. Method: Forty-four university students (age 20.36 ± 3.13 years) participated in this study. Two sessions were conducted, one based on a standard rules 1 × 1 basketball situation (“practice to maintain”) and one with motor, temporal and spatial restrictions in 1 × 1 tasks (“practice to learn”). Results: “Practice to learn” produced a higher perceived mental load (NASA-TLX scale) and a worse performance than “practice to maintain”, but was moderated by experience and inhibition (p = 0.001). The same happens in the most demanding restriction (i.e., temporal, p < 0.0001). Conclusion: The results showed that increasing the difficulty of 1 × 1 situations through restrictions harmed the player’s performance and increased their perceived mental load. These effects were moderated by previous basketball experience and the player’s inhibition capacity, so the difficulty adjustment should be based on the athletes themselves.