Complex sentence: Damas made his professional debuts with Sporting Clube de Portugal aged 19; after two years as a backup, he became the capital side's undisputed starter, winning two leagues and three cups, including the double in 1973--74.
Split into simpler sentences: Damas made his professional debuts with Sporting Clube de Portugal aged 19. After two years as a backup, he became the capital side's undisputed starter, winning two leagues and three cups, including the double in 1973--74.