Goalkeeper Jake Eastwood has joined Chesterfield on an emergency seven-day loan deal, subject to final approval.
The 21-year-old has moved to the Proact Stadium with immediate effect and could make his debut at Stevenage on Saturday.
The Spireites currently have first choice Joe Anyon out with a broken arm, whilst Tommy Lee retired last month having failed to recover from a serious shoulder injury.
Eastwood is expected to take the place of Wednesday stopper Cameron Dawson, who recently made two appearances for Chesterfield prior to being recalled by his parent club earlier this week.
Blades chief Chris Wilder commented: "We are happy to be able to help Jack (Lester) and it is an opportunity for Jake to go and play at a competitive level."