The Spireites' first defeat of pre-season on Friday came thanks to a well-taken finish from Nathan Arnold just before half-time and a winner by an Alfreton trialist, who punished a poor clearance from substitute goalkeeper Richard O'Donnell.
Danny Whitaker had put Sheridan's side back on level terms in the second half but the home side took the spoils despite the League Two outfit creating the better chances.
Sheridan told Spireites Player: "Just like at Telford we created a lot of chances.
"I'd like to have scored more goals and made it easier for ourselves but I think it's important we get these silly mistakes out of the way because the goals we have conceded are not goals we should concede and we need to get it out of our game."
