Castro, who was available for Saturday night's game against the Montreal Expos, gave a brief statement but refused to answer questions.
"I just want to say I apologize to the team, the organization, especially my teammates, and my family," he said. "And that's all I have to say. And I'm innocent."
Asked why he was apologizing if he was innocent, Castro said, "I am innocent" as he was led away by a team official.
Manager Jack McKeon said he wouldn't hesitate to use Castro, who entered the game hitting .289 with three home runs and six RBI.
"If we should happen to have a situation where we need him, we'll definitely use him," McKeon said.
A 28-year-old woman accused Castro of assaulting her in the player's hotel room following Wednesday night's game in Pittsburgh, police said.
According to court records, the woman told police Castro threw her on a hotel bed, pulled off her clothes and held her down. The woman tried to push Castro away and told him to stop, but he
continued to sexually assault her, the documents said.
The woman went to a hospital early Thursday morning, and staff members there called police. The woman was treated and released for what police described as minor physical injuries.
A preliminary hearing is scheduled for Thursday.