A day after announcing Nyman had been hired for the new post, the embattled federation announced in a statement posted on Twitter that his "employment will not continue due to a conflict of interest".
No other details were given, nor was there any indication of why the conflict was not discovered during the hiring process.
It's the third time since August that someone hired by the federation has lasted less than a week.
Mary Bono resigned after four days as interim chief executive after an outcry led by Olympic stars Simone Biles and Alexadra Raisman.
Bono had taken over from chief executive Kerry Perry, who had resigned after just nine months after criticism of her performance by USOC.
Perry's departure came after the appointment and swift resignation of elite coach Mary Lee Tracy -- who had made comments supportive of Nassar in 2016 when allegations of abuse against him had begun to emerge.
Nassar has been jailed for life for the abuse of more than 250 athletes, including several stars of the United States' gold medal-winning teams at the 2012 and 2016 Olympics.
The federation has declared bankruptcy as it faces lawsuits from Nassar victims, and the US Olympic Committee had threatened to decertify it as the sport's national governing body for failing to reform in the wake of the scandal.
The latest mis-step comes less than two months after Li Li Leung, a former NBA executive, took over on March 8 as president and chief executive.
Source: AFP
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