The winger, who scored the opener against USA, is gutted at how the Seleccao allowed Jurgen Klinsmann's men to get back into the game despite their own late equaliser
The Manchester United forward put the Seleccao ahead early on but a stunning equaliser from Jermaine Jones and a poacher's finish from Clint Dempsey looked set to dump the Euro 2012 semi-finalists out of the competition with a game to go.
However, Silvestre Varela's headed goal from Cristiano Ronaldo's pin-point cross changed their fate - at least temporarily - but Nani admitted afterwards that the mood is very much one of deep disappointment in the dressing room.
"We are disappointed," the 27-year-old told RTP. "We wanted to win the game to feed our World Cup dream. Now, it's harder, and there is a lot of grief within the squad.
"We gave USA a tough game. Now we must rest and see what we can do next. We are aware that it is very difficult. We all must do our best. We came to Manaus to win, but we were overwhelmed in the second half. Then it was complicated."
If Germany and USA (both on four points) draw, Portugal and Ghana (both on one point each) cannot go through should they win, while a victory in both games could see one of the current bottom two teams pounce for second place in Group G.
Portugal's awful goal difference - they were beaten 4-0 by Joachim Low's men in their opener - means that they realistically need Germany to beat USA by a healthy margin while giving Ghana a similar treatment on Thursday.