Danish X-Files podcast Sammensværgelsen (The Conspiracy) digs into the process of finding the right actors with Rick Millikan, the casting director for The X-Files. He's been involved in the casting of every single episode, except for the pilot.
It was a well-kept secret that Clive Owen was interested in being on The X-Files. While Daphne Zuniga (Melrose Place) was one of the few choices for Monica Reyes, Millikan explains that when auditions began for the casting of her partner John Doggett he remembered "Chris Carter meeting with Clive Owen. He was somebody that was interested, and we were interested in meeting with him." In the early 2000s, Owen was just breaking through the film industry and making a name for himself in the action genre. When Millikan and Carter discussed the possibility of casting him as John Doggett there was a discrepancy in the way that they wanted the character to present themselves and whether or not Owen could do it.
The special agent who Robert Patrick portrayed had a stern and forceful presence. According to Millikan, "after we met him [Clive Owen], I remember Chris ultimately thought that he wasn’t the right guy because he wanted more of the cop that Robert ultimately was. You know, he got that hard edge to him, and that I think Chris was really looking for." While they did pass on the actor, Millikan fondly spoke on "meeting Clive and thinking that was kind of cool because he was just becoming a hot ticket back then, but he just wasn’t the right guy."
Full podcast below:
Sources: Screen Rant, Sammensværgelsen