The phrase "serious setback" means a significant or big obstacle or problem that causes a delay or a negative impact on progress or success. Full definition
Initial gene therapy efforts suffered serious setbacks in the 1990s when patients in several clinical trials developed treatment - related leukemia and a young man in another trial died from his treatment. (sciencedaily.com)
Many couples experience what feels like serious setbacks in their relationship at the onset of a child. (trisf.com)
But I've never heard of there being a case of serious setbacks or career - ending for shoulder injuries. (sbnation.com)