Shang has been recovering from a nasty bout of fever and wasn't able to train for nearly five days ahead of China's debut, a wobbly performance for a team that has hoped to regain the podium in Rio after relinquishing the gold medal to the U.S. women's team at the 2012 London Games.
Though far from perfect, China are well placed to reach Tuesday's team final, where a U.S. team led by world all-around champion Simone Biles are the favourites.
During her illness, Shang had thought that she might have to relinquish her spot on China's team in Rio.
''I was worried because the coach said that I might get replaced on the team since I had a fever,'' Shang, who is also expected to make the cut for the all around final, said on Sunday.
She said the qualifying performance -- where her vault was shaky and drew a low score of 12.766 -- wasn't up to her standards and had been affected by nerves.
''I feel regret because I didn't perform well. If I performed more bravely, then I would have done better,'' Shang said.
Team China provisionally topped qualifying with a total of 175.279 points, but are likely to slide down the rankings once world champions United States perform later on Sunday.
None of the scores from Sunday carry over to Tuesday's team finals. In qualifying, four competitors from each country compete on each apparatus with only the top three scores counting towards the total. In the final, each nation will put forward three athletes and all three scores will count.
It wasn't the first time Shang has overcome difficulty on her path to the Olympics.
Growing up in poverty in rural China, Shang's parents couldn't afford to hire a coach for her, and her visually impaired brother made a deep sacrifice.
''My brother did a lot of things for me. I lived in the countryside. I needed a coach, but we didn't have any money,'' said the 20-year-old gymnast.
''My brother gave up studying for me to do gymnastics. My dream is to find a way to cure my brother's eyes. I want him to see how beautiful the world is.''
(Reporting By Joshua Schneyer, editing by Neil Robinson)
