Alimi Ballard, Matthew Willig

Sometimes, even NCIS' Jethro Gibbs needs a little help cracking a case.

Check out photos of the NCIS cast

Apparently, the upcoming serial-killer story arc that will unwind over the remainder of the CBS hit's eighth season is one of those times. TVGuide.com has learned exclusively that Numb3rs star Alimi Ballard and former NFL journeyman Matthew Willig have been cast as two recurring NCIS agents who join our regular team in the hunt for a psychopath called the Port-to-Port Killer.

Willig plays Special Agent Simon Cade, a hulking but friendly federal agent with a photographic memory. But he's not all brawn: He has an Ivy League education to go along with his intimidating presence. Ballard plays Special Agent Gayne Levin, a weathered, well-traveled federal agent who's just happy to be back in Washington.

Both men are members of the team led by the recently introduced E.J. Barrett (guest star Sarah Jane Morris). And even though the trio is ready to pitch in on the case, don't be surprised if Gibbs (Mark Harmon), Dinozzo (Michael Weatherly) & Co. initially have some trouble sharing the squad room.

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The Port-to-Port Killer will be introduced in the April 5 episode, "Two-Faced." Ballard and Willig kick off their multi-episode run the following week in an episode titled "Dead Reflection."

Willig, 42, played offensive tackle for several National Football League teams. He's appeared on such TV shows as Dexter, Chuck and My Name Is Earl.

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Besides his work as David Sinclair on Numb3rs, Ballard, 33, has also appeared on Sabrina, the Teenage Witch and alongside NCIS' Weatherly on Dark Angel and the soap opera Loving.

NCIS airs Tuesdays at 8/7c on CBS.

Are you excited to see the new team members?