Actor William Petersen, who departed with his longtime role as Gil Grissom on "CSI: Crime Scene Investigation" last month, said he wasn’t sorry about leaving the show.

After playing the role of a forensic entomologist and night-shift supervisor of the Clark County, Nevada CSI (forensics) team, investigating crimes in and around Las Vegas, for nine seasons, William Petersen said the reason why he decided to leave the show was because he was afraid of becoming “too comfortable.”

“It's 'CSI' -- they pay me a lot of money, and I don't have to work very hard anymore. I've got it all figured out. And I just realized, God, as an artist, I'm going to atrophy,” Petersen told Entertainment Weekly.

Even though he admitted that shooting his last scenes was difficult, he said he won’t miss his character and hopes the audiences won’t miss him either. Petersen agreed to continue being an executive producer for the show and return for occasional guest appearances.

His co-stars on the other hand, didn’t handle his exit so well. Marg Helgenberger said he was traumatized when they taped Petersen’s last show last October and he “couldn't stop crying.”

“You do anything for nine years, it becomes somewhat rote. I didn't want to be on the show because they were paying me money and I liked the money. I didn't want to be on the show because it saved me from having to go look for other jobs. Just didn't want it. It was too safe for me at this point. So I needed to try and break that, and the way to do that, for me, is the theater."

Furthermore, Peterson revealed the secret of a good show which made a worldwide success of "CSI," which averages 21.3 million viewers per week. He said the key ingredients included "fabulous puzzles," "great chemistry," "courageous writing" and solid acting performed in a style slightly different from what people are used to on television.

The final episode starring Grissom, at least for a while, will air Thursday at 9 pm/ET on CBS. With Petersen as Grissom on the verge of leaving, the series introduced a new character, Ray Langston, a criminology professor/former research pathologist, played by “Matrix” star Laurence Fishburne.

In addtion to Fishburne's new character, country music singer Taylor Swift will appear later this season as a troubled teenager whose parents own a motel. The episode will start in the present, then revisit the last year, season by season.