"We went from the dream of a great victory to the nightmare of a terrible defeat," said coach Carlos Alberto Parreira.
Uruguay hit back to overturn Brazil's two-goal halftime lead and went 3-2 ahead before Ronaldo equalised late on to secure his team's second successive draw in the competition.
"It could have been worse. It would have been incredible to have lost this game after the amount of possession we had," he added.
Parreira counted 27 scoring chances for Brazil which logically suggested to him that they had done more than enough to win.
But logic has historically played little part in matches between the two sides.
Although Brazil's population is around 50 times bigger than Uruguay's, the world champions have always found their smaller neighbours to be tough customers.
The most infamous upset was the decisive match of the 1950 World Cup at Rio de Janeiro's Maracana stadium, when a seemingly invincible Brazil team lost 2-1.
More recently, Uruguay beat Brazil in the 1995 Copa America final and took four points out of six from them in the qualifiers for the 2002 World Cup.
The small contingent of travelling fans in Curitiba's Pinheirao stadium chanted "Maracana, Maracana" after the final whistle on Wednesday.
HALF ASLEEP
Brazil's players admitted that had they been half asleep as the second half got under way.
"It was a big lesson for all of us," said midfielder Ze Roberto.
Gilberto Silva, whose bizarre own goal briefly put Uruguay ahead, added: "We had the game in our hands but lost concentration and let them draw."
Earlier this month, Parreira said that the qualifiers were more difficult than the World Cup itself for Brazil and added that any European team would also struggle to get through the South American group.
Brazil lost six matches and used four coaches before finally sneaking into the 2002 World Cup finals with a 3-0 win over Venezuela in the last of their 18 matches.
This time, they made a smooth start by winning their first two games in the 2006 World Cup qualifiers away to Colombia and at home to Ecuador.
But Sunday's draw in Peru and Wednesday's extraordinary game point to another long, hard slog along the road to Germany 2006.
