NCIS actors Sean Murray and Wilmer Valderrama are reportedly vying for the leading role on the popular crime drama, as rumors swirl about the potential return of the show's biggest star, Mark Harmon.

Following Harmon's exit after Season 19, both Murray, 45, and Valderrama, 43, have enjoyed increased screen time and character development. However, sources say this has also led to growing egos and rivalry between the two.

"There's no denying Mark's departure gave their characters room to grow," an insider explains, "But you now have two actors who think they should be the star of the show."

Murray, who portrays Senior Field Agent Timothy McGee, has been part of NCIS since its first season, while Valderrama, who plays Special Agent Nicholas Torres, joined the cast in Season 14.

"Wilmer considers himself the primary star, but Sean has a bone to pick with that," shares the insider. "Sean likes to rub it in Wilmer's face that he's got higher billing in the credits. Wilmer's working to change that."

Although the two actors present a united front publicly, sources claim that they tend to irritate one another off-camera.

The competition for the spotlight may intensify if showrunners manage to bring back Harmon. As previously reported, Harmon has hinted at returning to NCIS as Special Agent Leroy Gibbs, a prospect that has even castmate Rocky Carroll stating, "We might see Gibbs again." Should Harmon return, both Murray and Valderrama will likely have to share the limelight once more.