Chang's test failure preceded a poor start to the Games by Taiwan
Taiwan baseball player Chang Tai-shan, who failed a pre-Olympics drugs test, has blamed fertility medication.
Chang told an International Baseball Federation (IBAF) hearing that he began taking the medication in 2007 to try and cure his infertility.
Taiwan's Olympic Committee delegation said in a statement that Chang had expressed his regret over the matter.
"It has hurt his personal image and the reputation of the (Taiwan) team and he deeply apologises," it said.
The IBAF has asked the player to report back to them with a complete medical history as soon as possible, it added.
Baseball is Taiwan's most popular sport and offers one of its few chances at winning an Olympic medal.
But the team has lost three of its four games so far, including a defeat on Friday to lowly-ranked China that caused shock among fans in Taiwan.