Hola Johan
In Spanish when you use verb "jugar" as in playing a sport/ game we use "al", "a la", "a los" or "a las":
"Juego al tenis" (I play tennis)*
"Juego a la pelota" (I play [with] a ball)
"Juego a los dados" (I play darts)
"Juego a las cartas" (I play cards)
*Note that here "al" is a contraction of a + el.
Un saludos
Inma
