The transition from Season 8 to Season 9 for "CSI' was a major one. Not only was Gary Dourdan's character killed off, but Jorja Fox also departed during that timeframe (via TV Guide). However, her character was kept alive, allowing her to continue making guest appearances throughout the show's remaining run as well as appear in the current spinoff series "CSI: Vegas." Dourdan wasn't as lucky, and while there isn't a ton of information out there concerning why negotiations fell through, Entertainment Weekly offered this tidbit: "According to an insider, the decision was a mutual one made by the actor and CBS/Paramount, the studio that produces the procedural drama for CBS."
According to reports, CBS didn't waste any time trying to find a replacement. TV Guide goes on to report how producers quickly sought actors for the role of Ray Santoro, which is noteworthy because a character by that name never ended up on the series.
Gary Dourdan may have permanently left the "CSI" franchise, but he hasn't done too badly for himself in the years since he left the show. He's appeared in a number of movies and TV shows over the years, most recently with a recurring role on "First Wives Club." Whatever the reason for his exit from "CSI," few could argue that he didn't receive one of the most emotional send-offs in the show's history.