The 25-year-old left the club at the weekend after asking to be released midway through a two-year contract following their relegation to National One.
Albion reluctantly granted Stagg’s request and he has since joined Doncaster Knights, where he will link up with former Plymouth players Declan Cusack, Tyler Hotson, Bevon Armitage and Tyson Lewis.
Although the former Rotherham and London Scottish player asked to leave Brickfields because he wanted to continue to play at Championship level, he is hoping Graham Dawe’s side have a successful campaign in National One.
“I would like to take this opportunity to thank everyone involved in my year at Plymouth Albion, particularly the supporters, in what proved to be a difficult season,” said Stagg.
“I would like to wish everyone at the club the very best ahead of the coming season.
“I am hoping to see the team promoted back to the Championship as soon as possible.”
Fellow hooker James Penman, who joined Albion towards the end of last season, is set to stay at the club, while Dawe is expected to make further signings in the coming days.