The Blues boss has signed left sided midfield player Tyler Williams from Goole AFC.
Williams like full-back Ashley Jackson is based in Sheffield and came through the Sheffield academy. He has also had a spell at Worksop Town and has made 30 appearances for The Vikings this season scoring 3 goals.
The 19-year-old plays wide on the left and Casswell says he will give the team some pace out wide.
"He's played against us for Goole and was the stand-out player. He's got pace and will give us another option out wide."
Casswell has also made 7-day notices of approach for several other players and hopes to secure further signings before the transfer deadline next Thursday.