Agassi, now 44, won the Wimbledon singles title in 1992 and went on to claim four Australian Open titles, two US Opens and the French Open in a glittering 20-year career.
Despite the flashpoint, the former child star and the tennis champion wed in April 1997.
It would be another two years before they divorced just shy of their second wedding anniversary but Shields wrote that it didn't take her long to wish she'd never gone through with the ceremony.
The day after the wedding in Big Sur, California, she realised she had made a 'mistake.'
'I could not form a sentence. I kept shaking my head as if I had duct tape across my mouth. It hit me all of a sudden - I knew I had made a mistake. I did not want to be married… I wanted to be a bride but I shouldn't have been married yet,' she wrote.
The couple were busy working apart for much of their marriage and Shields said the relationship was 'just existing.'
