The pair were linked to using performance-enhancing drugs during an undercover report by Al Jazeera late last month. As part of the investigation, pharmacist Charlie Sly said he supplied the two with the hormone supplement Delta 2, which is listed on MLB's banned drug list.
"Mr. Zimmerman has never taken Delta 2, human growth hormone, or any other steroid or other performance-enhancing substance banned by the MLB," Zimmerman's lawsuit states.
Howard said that he authorized his attorneys to file suit against the broadcaster in order to preserve his image.
"I authorized my attorneys to file suit against Al Jazeera and its reporters," Howard said in a statement. "Their irresponsible reporting forced me to take this action to protect my name and to fight back against the spreading of these lies."
Sly would later recant his statements prior to the report airing. The Nationals followed by issuing a statement standing behind Zimmerman, saying that they do not find Al Jazeera's report credible. The Phillies issued a statement of their own, claiming Howard vigorously denied the allegations.
William Burck - the attorney for both Zimmerman and Howard - threatened legal action on Dec. 30. Al Jazeera has stood by its story, but Burck notes the online report initially claimed Howard and Zimmerman received Human Growth Hormone. The copy has since been amended to say the substance was Delta 2, and not HGH. Burck believes, however, that Al Jazeera should be held responsible for what he deems is careless reporting.
MLB announced it plans to conduct a thorough investigation of the information.
Denver Broncos quarterback Peyton Manning was the centerpiece of the report from Al Jazeera. Manning has adamantly denied any ties to using PEDs or HGH and has pledged to fully cooperate with the NFL's own investigation.