The 22-year-old knows anything can happen in football and he is hoping for an incredible turnaround against the Bundesliga champions on Wednesday
The Catalan club were blown away in the Allianz Arena as the Germans put four past them without reply but the 22-year-old is still hopeful Tito Vilanova's charges can overturn what seems an almost insurmountable deficit.
"I think we will make a comeback," he told the club's official website.
"We're in good condition and we have a team that always want to win, but anything can happen in football."
The Camp Nou outfit were held to a 2-2 draw by Athletic Bilbao on Saturday in what was the Basques' final game at San Mames before it makes way for their new stadium.
And Thiago paid tribute to their ground and believes their new home will be just as good.
He said: "San Mames is a historic stadium and we've always really enjoyed playing here, but I'm sure the new stadium will be great as well."
Alexis Sanchez was among the scorers as Barca edged closer to the Liga title and the Chilean knows the value of having a fit Lionel Messi for the Champions League clash against Bayern as the Argentine came off the bench to score and assist in Saturday's league encounter.
"We know what it means to have Messi on the pitch, it doesn't surprise us, when he comes in, he changes the game," he said.
" [Against Bayern] we need to fight back, but we also know it will be very difficult."
The second leg of the semi-final is scheduled to take place on Wednesday, May 1 at 20:45CET.