When Megyn Kelly jumped ship this week from Fox News to NBC, very few people were surprised; after all, her long-standing feuds with Donald Trump, Sean Hannity, and Rupert Murdoch were highly publicized. She frequently drew the ire of leading conservative pundit Mark Levin and, of course, there was that infamous sexual harassment scandal involving ex-CEO Roger Ailes that Kelly wrote about at length in her recent autobiography, "Settle for More."

However, according to an unnamed source at Fox News, it appears that the colleague Megyn Kelly aggravated the most was Bill O'Reilly, host of the highly-rated show "The O'Reilly Factor." Gabriel Sherman, a writer for New York Magazine, recently revealed that O'Reilly didn't merely dislike Megyn Kelly-- he downright "hated" her.

Unidentified Fox host describes tensions

In a New York Magazine article published on January 3, Sherman was told by an unnamed source-- identified in the article as one of the network's hosts-- that Kelly's working relationships with Bill O'Reilly and Sean Hannity had "completely broken down" by the time of her book release. "Bill hated her," said the unnamed Fox News host to Sherman.

O'Reilly throws shade at Kelly

As far back as November, O'Reilly was taking advantage of his coveted prime-time slot to throw the occasional veiled jab at Megyn Kelly. While the former host of "The Kelly File" was busy making the rounds on her book tour-- at the height of the controversy surrounding her sexual harassment accusations against Roger Ailes-- O'Reilly ended the November 15 episode of his show by lecturing his audience on the importance of remaining loyal to your employer.

"If somebody is paying you a wage, you owe that person or company allegiance," said O'Reilly, without mentioning Kelly by name. "If you don’t like what’s happening in the workplace go to human resources or leave."

According to Sherman, Kelly will be hosting a daytime "Oprah-like" talk show on NBC as well as contributing to the network's political coverage.