Defamation is a gray area. There is clear defamation, where a statement is made to be fact. "Tiger Woods used PED's and is currently suspended."
Then, there is opinion, where the speaker clearly states he is making an opinion. "I think that Tiger Woods used PED's, and that's why he is suspended."
Olsen managed to straddle the extremes and find the gray area that lawyers, both prosecution and defense, love: "
I heard from someone credible
that Tiger Woods used PED's." This could very well be a fact: Dan Olsen very well could've heard that Tiger Woods used PED's. He could've heard it from a neighbor, his wife, or from another burned out former Tour player. Now we have to define "someone credible." See where this is going? Who did you hear it from, Mr. Olsen? "Uh, I don't recall."
Since Olsen prefaced most if not all of what he was saying with basically "someone credible told me that...", then he is not making a statement himself. It could be argued, from a defense standpoint, that Olsen was passing along gossip. Gossiping is not against the law if Olsen's defense can make a reasonable assertion that Olsen did indeed hear the rumor, and that Olsen had the slightest reason to believe that an athlete could very well be using PED's.
What we can draw from this is that Olsen is an idiot, Tiger should sue anyways, and I'm not allowed to call my lawyer buddy during office hours any more because he's "on billable hours, douche."