Marty Deeks (Eric Christian Olsen) was one of the main officers on the NCIS: Los Angeles team, and though he was a fan favorite, it’s unlikely Deeks is ever going reappear in another NCIS show. There have been eight spinoffs of the NCIS franchise and NCIS: Los Angeles premiered in September 2009 and lasted for 14 seasons. Like the other shows in the NCIS franchise, NCIS: Los Angeles follows the Naval Criminal Investigative Service in the Los Angeles area, which generally puts them in contact with Cartel elements and problems across the border.

https://screenrant.com/deeks-ncis-eric-christian-olsen-wont-return/