The 66-year-old coach felt that the Copa America holder could have upset the home side had the team's No.10 not failed to convert from the spot early on.
The Copa America champion was awarded a penalty just 14 minutes in when David Luiz pulled down Diego Lugano in the area, offering the underdogs an opportunity to take advantage of a very nervy start from the home side.
However, Forlan's spot kick was saved by Julio Cesar and although Uruguay looked set to force extra time, with Edinson Cavani cancelling out Fred's opener, the team ultimately succumbed to an 86th-minute header from Paulinho.
"I don’t like to talk about ifs and buts, but what I can say is that when we missed that penalty we gave Brazil the shot in the arm they’d been lacking up to that point," Tabarez told FIFA.com. "You just have to accept results, though, and we accept this defeat.
"That said, we could have taken the game into extra time and we even had chances to win it. I’m going away a proud man, though, because I know that if we can play like that, we can give anyone a game."
Uruguay will now meet the loser of Thursday night's clash between Spain and Italy in the playoff for third place in Salvador on Sunday afternoon.