This is a hypothetical situation and the question is based on this:

So, A professional baseball player brings a defamation action against his former personal trainer and an online sports-news website based on a news article on the website that the baseball player used performance-enhancing drugs. The baseball player is also suing the website based on alleged defamatory statements posted by anonymous Internet users in the comments section attached with the article. The personal trainer also made statements to the FBI as part of a federal grand jury investigation involving the use of performance-enhancing drugs. The former trainer stated he has videotape evidence of drug use that he turned over to the FBI.

To establish a defamation claim the professional baseball player will have to prove typically four elements, describe the four elements and how our baseball player will establish them.