Stuart Pearce said a lack of confidence within the Nottingham Forest squad allowed Rochdale to register a 1-0 win and pull off one of the shocks of the FA Cup third round.
Peter Vincenti's first-half spot kick proved enough for Keith Hill's League One side to book a place in the fourth round of the competition for the second year running.
Forest bossed the second half but failed to carve out any clear-cut chances as the home defence withstood their pressure.
Pearce said fortune is not favouring his players right now.
"I felt with the effort the players put in, especially in the second half, we deserved something out of the game but the nature of where we are at the moment means we're not getting the rub of the green," he said.
"We've gifted the opposition a goal with a very soft penalty and our decision-making under pressure has cost us in that respect.
"Apart from that we've dominated the game and had a host of efforts and skirmishes, especially in the second half, but we failed to create a goal from that.
"In the first half Rochdale showed enough endeavour that when you make mistakes as we did in our own box then it is going to cost you.
"I don't want to take any credit away from Rochdale, I've played in the FA Cup as a non-league player against league opposition and you take whatever you can get.
"It was one of those games where we couldn't get a clear-cut opportunity and credit to them, they are in the next round and good luck to them."
Forest started well enough with Dale goalkeeper Josh Lillis called into action to block a David Vaughan free-kick, but the home side took the lead in the 12th minute. Referee Gary Sutton pointed to the spot when Danny Fox brought Joe Rafferty down and Vincenti slotted home the penalty.
Forest had chances in the second half but Chris Burke glanced a headed attempt wide and Britt Assombalonga was denied firstly by a Lillis save and later a block by defender Ashley Eastham. Lillis pushed a late header by Lars Veldwijk over the bar as the home side stood firm.
"It was a very competitive, quick game and after we'd scored the penalty we had a couple of really good chances and didn't put them away," said Rochdale assistant boss Chris Beech.
"At 1-0 the game is always on the edge and the lads defended resolutely in the second half.
"We didn't look in too much danger but the Forest players are so talented, there was millions of pounds worth of talent out there, a massive void in finance between the clubs and the standard they play at.
"But from our point of view there was six players in the squad who represented the club in the FA Youth Cup three years ago and to play in the FA Cup made me and the management team immensely proud."
Source: PA
