The host nation were sensationally dumped out of the tournament on Tuesday night with a 7-1 defeat in Belo Horizonte.
"It's hard to come up with an explanation," Willian told FIFA.com. "Everything came off for them and everything went wrong for us.
"We're still trying to come to terms with it, though sometimes there are things that happen in football that have no explanation."
Brazil play their final game of the tournament on Saturday against either Argentina or the Netherlands in the third-place playoff.