Danny Wilson was a disappointed manager after his Chesterfield side tossed away a half-time lead before losing 3-1 at Rochdale in the EFL Cup first round.
Some questionable defending ultimately cost the Spireites, with Ian Henderson, Andy Cannon and Nathaniel Mendez-Laing profiting after Paul McGinn had scored a spectacular opening goal in the first half.
Wilson said: "It was frustrating more than anything. I think we caused Rochdale a lot of problems in the first half, which was good.
"We went in at half-time buoyed, but lo and behold, we give a cheap ball away, then a poor free-kick away, and we're chasing the game.
"Rochdale is always a tough place to come, but when they've got their tails up, they're a good side.
"You can't under-estimate them at all.
"We've just been victims of our own bad play at times.
"For 45 minutes we've more than matched Rochdale, but we've conceded two bad goals.
"These things happen, but we just have to make sure it doesn't happen when there's similar circumstances.
"The two goals that have effectively cost us the game have been down t ourselves and we have to cut that out.
"We have to learn from it. I won't accept any excuses, these players are in the team to play and they've got lessons to learn.
"They need to learn quickly though."
Spireites defender Ian Evatt took a nasty bash to the head in the second half at Rochdale, but should be okay for the weekend.
Rochdale 3 [Henderson 47, Cannon 53, Mendez-Laing 78]
Chesterfield 1 [McGinn 31]