Big shake up in the aging CBS crime lab at CSI: Crime Scene Investigation: Two of the lead investigators will be scarce next season.

Laurence Fishburne has decided not to renew his one-year contract to play Ray Langston, who killed his crazy nemesis, Nate Haskell, at the end of the show's 11th season last month. Bill Irwin created one of TV's best villains with the Haskell character, and, sad to say, his serial killer was more compelling than Langston, who never caught on with the still-entertaining CSI and made veteran viewers pine for the return of William Peterson's Gil Grissom.

Marg Helgenberger, whose Catherine Willows character has been with the series for all its 251 episodes, announced months ago that she would reduce her role to recurring in 2011-12.

The contracts of other beloved, George Eads (who plays Nick Stokes), Jorja Fox (the endearingly enigmatic Sarah Sidle), Paul Guilfoyle (brassy Capt. Brass), Robert David Hall (medical examiner Al Robbins) and Wallace Langham (who brings just the right ewwwww-factor to lab rat David Hodges), are in various stages of negotiation. Not sure who-all will be back.

Speaking of EW, executive producer Carol Mendelsohn told Entertainment Weekly's Lynette Rice here that the series is accustomed to uncertainty: "We always start planning for next season without knowing for sure" who will be returning.

Viewer fatigue and the absence of Grissom has pulled the show from its once-dominant ratings position. It finished 11th this season in the Nielsen category of Viewers 2+ (they figure ads don't work if you can't talk), and 30th among the 18-49 year-old crowd.

Those numbers are far from shabby, but I'm hoping they reinvigorate the whole thing as it moves to Wednesdays at 10, and that it sticks around for another 11 years.