STEVE McClaren felt his Derby County team were dealt a "harsh lesson" in Saturday's 3-3 draw with Birmingham City.
The Rams went behind but led 3-1 at St Andrew's with only 12 minutes remaining.
However, the home side hit back to snatch a last-gasp point as Derby missed the chance to go third in the Championship table.
"We should have won it easily and instead we ended up drawing, so that's a disappointment," said McClaren.
"It's a harsh lesson for our team.
"At 3-1, we lost our discipline and didn't control the game.
"We just went for it and a game we could have won 4-1, 5-1 or 6-1 ended up a 3-3 draw."
Craig Bryson saw his penalty saved in a goalless first half and Brian Howard put Birmingham ahead against the run of play soon after the break.
Derby hit straight back through Patrick Bamford and took the lead courtesy of a fortuitous strike from Bryson.
Craig Forsyth added a third for the Rams but Chris Burke pulled one back for the Blues on the counter attack shortly afterwards.
Then, in the third minute of added time, debutant Federico Macheda equalised for Lee Clark's side.
"The second goal we conceded was an absolute disgrace,"McClaren added. "It was a terrible goal. When we lost possession we had six players in front of the ball, Lee Grant saved from Macheda but we failed to defend the loose ball and Burke scores.
"It's cost us. We've missed a great opportunity in a game we should have won but that's football."
