Speaking to Esquire in a recent interview, the 42-year-old confirmed that the new spin-off will tell the story of Jamie's parents, Ellen and Brian Fraser.
WATCH: Have you caught up on series six?
When asked what he could reveal about the series, he said: "All I can tell you is I'm not in it, as Jamie's not in it!
"I believe that it's a prequel focusing on Jamie's parents when they were younger, so I guess you might see a young version of him at some point. But I think I may be a little too old to play young Jamie now! I could play his dad maybe, or a flash forward? It is time travel, after all."
While it may seem an obvious assumption that Sam would be absent from the series as it is set to focus on Jamie's parents, the actor previously revealed that he hoped to "get in" to the new series in some way.
Sam confirmed that he will not be in the prequel series
Chatting on the Happy Sad Confused podcast back in March, Sam explained: "I knew it was in the wings, I knew that was happening, I didn’t realize it was so far advanced.
"I saw Diana this weekend, and she was writing furiously. And I know they're really excited. I'm excited for them, and I'm slightly jealous as well. I wonder if I can get in there."
Back in February, Variety reported that a writers' room was being assembled and pre-production was due to start in a matter of weeks.
Matthew B. Roberts, who serves as showrunner on the main series, will take the helm as writer and executive producer, alongside Maril Davis and Ronald D. Moore, who developed the novels of Diana Gabaldon for television.
Sam plays Jamie Fraser in the series
Diana is currently working on her own prequel project - a new book which will tell the love story of Ellen and Brian Fraser.
The writer teased what could turn out to be the opening line of the book in a Facebook post back in February.
She wrote: "Ellen MacKenzie, eldest of the children of Jacob Ruadh MacKenzie, chief of Clan MacKenzie—well, the late chief, if only by moments, but she'd think about that later—grabbed Ailidh Watt from behind and dragged her out of sight, clapping a hand over her slobbering mouth to stifle her cries.'"
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