Frecks picked up an ankle injury in the 3-0 defeat at Leeds 10 days ago and now faces another month or so on the sidelines.
Speaking to Radio Sheffield, boss Paul Warne said; "It's a massive blow and he's very upset about it. I've got midfield options but I don't make any secret of the fact that he's the most important player of the team. 'He's got energy, he keeps running, gets the crowd on their feet and helps the team go forward."
"If I looked at the performances this season with and without him I'd be surprised if we haven't performed better when he's been in the team."