Holland said he didn't do it and the only other person he knows that has access to his account -- @Dutch_Oven45 -- is his fiancée, Lauren. The slur appeared in response to a fan heckling Holland on Twitter.
"I know it wasn't myself," Holland said. "I talked to my family and my fiancée and they all said the same thing -- that it wasn't them. I know MLB is taking care of it and helping me out and figuring out who it was."
Holland, who by MLB rules is not allowed to tweet within 30 minutes of the first pitch and during games, was told of the tweet after the game. He was on the mound for nearly seven innings and didn't know anyone was sending tweets out from his account.
"We take something like that very seriously. It's not a term or sentiment we endorse in any way," general manager Jon Daniels said. "We asked Derek about it. He was not aware of it happening. We alerted MLB about it so that while we do our own investigation, they can do one as well.
"Nobody has admitted to doing it, so we don't know if it was somebody who had access to the account appropriately or if it was a hacker, but we're leaving that up to the investigators to figure it out."
"I'm pretty upset with the whole situation and me being accused of something I haven't done," Holland said. "In case you haven't seen, all I ever do write Chuck Norris facts or random facts, 'a pig or a duck, you can't hear its echo.' I don't ever write anything like that."
Holland has nearly 93,000 Twitter followers. He said he hasn't "messed with the whole Twitter since."
Holland doesn't expect to receive any discipline from MLB.
"I hope not," Holland said. "I didn't do anything. I shouldn't."
Information from The Associated Press was used in this report.