Former Saints duo secure Championship moves
Prop Davis has rejoined Ealing Trailfinders on a permanent basis having spent time on loan there after leaving the club for Saints in the summer of 2018.
Davis made seven appearances for Saints, while Mitchell played eight times during the 2019/20 season.
Mitchell will be hoping to fill the void left by Tom James, the scrum-half who is joining Saints from Doncaster this summer.
“I feel like Doncaster will be a great place to play rugby next year and the style of rugby we are looking to play suits me and my game," Mitchell said.
“I’m really excited to play for a club with such potential and hopefully I can become a real asset for the Knights.
"I’d also like to thank the Doncaster board for being very supportive during this uncertain time.”
Meanwhile, Saints double-winner Sam Dickinson has seen his stay at Ealing come to an end as he leaves the club this summer.