Translation:I was a soccer player many years ago.
You can use the preterite to refer to a long period of time in the past. Note this entry regarding Pablo Picasso from the Spanish Wikipedia.
Pablo Ruiz Picasso (Málaga, 25 de octubre de 1881-Mougins, 8 de abril de 1973) FUE un pintor y escultor español, creador, junto con Georges Braque, del cubismo.
Here, the preterite is basically required because you defining an entire time period by giving starting and ending dates.
However, even without a specific time period you can say that someone was a teacher or a football player and by using the preterite you emphazize that they are no longer. The this phase of their life is over. You don't have to state the exact length of time. It is also ok to use the imperfect in cases like this.
hacer + time period can be used for several different meanings, depending on the verbs used.
Yo fui jugador de fútbol hace muchos años.
I was a soccer player many years AGO.
Yo soy jugador de fútbol desde hace muchos años.
I have been a soccer player for many years. (meaning I still am)
Yo era jugador de fútbol desde hacía muchos años.
I had been a soccer player for many years.