The Euro 2012 finalists had taken a 2-1 lead in Sofia but were pegged by Georgi Milanov's second-half equaliser.
It was not the start the Azzurri wanted in Group B, and Prandelli is keen to see a much improved performance on Tuesday night when they take on Malta in Modena.
"The way we played in Sofia wasn't good enough," he said in a press conference. "It was too negative a performance.
"It's logical that the media didn't give the players high marks for their performance. We were as stretched as we've ever been in my two years as coach of Italy.
"This shows that the things you learn on the training ground can quickly be forgotten.
"We played the ball in the air far too much - far too many times. We conceded 10 corners and came under a lot of pressure.
"We looked vulnerable and weren't well organised tactically. And we didn't play with much quality either.
"I had tried to warn everyone about just how tricky this game was going to be, but, sometimes without realising it, it can happen that you just lack that extra bit of pace you need to get to the ball first."
Malta should, on paper at least, be slightly easier opposition for the Italians and Prandelli is unlikely to make too many changes to the side which failed to take maximum points in Bulgaria.
He will be without influential midfielder Daniele de Rossi, however, after the Roma man limped off in Sofia.
Italy are a familiar foe for Malta coach Pietro Ghedin, who hails from the country and was formerly an assistant coach with the Azzurri.
The Maltese began their qualifying campaign with a narrow 1-0 loss at home to Armenia last Friday and defender Andrei Agius is aware the odds will be heavily stacked against them on Tuesday.
"This has to be the biggest game of my career so far," he told local newspaper The Times.
"Italy did very well in Euro 2012 where they reached the final against Spain and are currently sixth in the FIFA rankings.
"I'm looking forward to the game as Italy are one of the best teams in the world. We have to be objective about our targets for the match as we all know what we're in for.
"If this game doesn't motivate you as a footballer, then you've got a problem.
"I'm preparing myself like I do for other games," the 26-year-old said.
"We have to remain concentrated all 90 minutes because this will be a very difficult match.
"After Bulgaria, Italy will be more determined to beat us in Modena and that further complicates our task."