“We have done our homework — me, Chris, Karl, we have done our jobs,” McDermott said. “But the players haven’t done theirs for the first time in seven or eight weeks.
“Just because they had gone seven unbeaten (does not mean) I am going to lay off the players.
“l’m on the case and if they don’t do it back-to-back then someone else will come in.”
Six injuries meant manager McDermott had to make changes, including a debut for new midfield signing Kegan Etherington.
One of his first tasks was to clear off the line from Shane Henry. No-one though could prevent Henry from giving the Moors a 25th-minute lead with a downward header from a right flank corner as Alfreton again succumbed to a set-piece.
Etherington fired against the post from a difficult angle two minutes after the Reds conceded.
A needless penalty in the 85th minute settled the issue after Jennings brought down Robert Ramshaw.
Chris Elliott was sent the wrong way from the spot by Joe Tait.
In the third minute of added time a Brendon Daniels delivery from the right saw Ryan Jennings smash the ball against the underside of the bar, with Tom Allan heading home from the rebound.
Allan then unleashed a thunderbolt narrowly past the upright as the Reds almost snatched a point.
McDermott added: “l thought Tom Allan was absolutely outstanding today — not only was he my best defender but he was my best footballer.
“He could play, he got it down, passed it, went up front and scored a goal — he had shots. He has done more than what my forwards have done.”
The manager said he thought the Reds were flat.
On Spennymoor’s first goal, McDermott added: “We said the main thing was going to be set pieces. It would be vital to be switched on.
“We had two spare men and we said be sure if you get picked up — but he walks in, a free header and it goes in.
“It doesn’t matter if you are a top level footballer, if you switch off goals are going to cost you matches and that’s what set pieces are.
“In the second half you would expect us to go out and pass it around, but we huffed and we puffed and that was about it.”
The clearest chance for the Reds came in the opening few seconds, but Ricky German hesitated when presented with the ball by Craig Disley’s lob over the top.
McDermott said: “We were toothless up front. Ricky in the first minute has got to score.
“l’m not just picking on Ricky but, as a team, as a forward they have got to work harder and make sure.”
“Westy is playing on his own at the moment - he needs help.
“If the first chance goes in it changes matches doesn’t it?
“That sloppy miss epitomised it for me.”
SPENNYMOOR: Porter; Griffiths, Mason, Dixon, Tait, Chantler, Taylor, Foley, Ramshaw [Andrew Johnson 87], Henry [Chandler 85], Anderson [Fewster 68].
Other subs: Curtis, Lowson.
ALFRETON: Elliott; Topliss, Shiels, Allan, Wood, Jennings, Disley [Marshall 68], Etherington, Daniels, Westcarr [Robertson 78], German [Sharp 57].
Other subs: Andre Johnson, Evans.
Referee: Mr. L.Doughty.