Direct Opposites:
* Sedentario/a: This means sedentary, someone who doesn't engage in physical activity.
* Inactivo/a: This means inactive, someone who doesn't participate in sports or exercise.
More nuanced opposites:
* No deportista: This simply means "not an athlete" and is a direct negation.
* Aficionado/a a otras actividades: This means "someone who is passionate about other activities," implying they are not into sports.
Ultimately, the best opposite for "deportista" depends on the specific context of your sentence.