The 22-year-old Eden, once hailed as England's answer to Australia star Billy Slater, was criticised for gifting Castleford two tries in Rovers' 26-22 Super League win on Sunday but will keep his spot for the Good Friday derby against Hull FC at the KC Stadium.
"Greg and I have a really good relationship," Sandercock said. "He knows what I think. He's a young kid who's getting better every day. Last year was his first in first grade. He's got an awful lot to learn and he's learning every day."
He went on: "There were a couple of key errors there but I thought he improved in a lot of his key performance indicators that I give him every week and he'll be better for it."
Castleford seized on the former Huddersfield player's defensive blunders but, with his elusive footwork and one-handed ball carries, Eden is seen as one of Super League's most potent attacking full-backs.
It was during his first full season in Super League that then Huddersfield coach Nathan Brown compared him to Slater, the Melbourne, Queensland and Australia full-back.