Kluwe and King had been involved in friendly competition for the Raiders job during training camp, with the veteran Kluwe reportedly offering King advice throughout.
The 31-year-old took to Twitter to confirm the news of his release and also took the chance to reassure fans that King was more than capable of stepping up to the mark.
"Thanks to everyone at the Raiders for the opportunity this pre-season. It was a blast. Marquette King's got a bright future with you guys!" Kluwe tweeted. "Feel like we both had a pretty strong pre-season. No regrets."
Kluwe joined the Raiders during the off-season after his seven-year spell with the Minnesota Vikings came to an end earlier this year.