Joachim Low’s side are considered to be amongst the favourites to lift the Henri Delaunay trophy but Muller insists it’s imperative they get that first win under their belts.
With tough games Holland and Denmark coming up after they’ve faced Portugal the 22-year-old is worried about the potential consequences of losing to Paulo Bento’s side.
“Making a good start is crucial because you avoid a pressure situation with the game against Holland,” said Muller
“We don’t want to go into the Holland game, against a nation who finished second at the last World Cup, with a bad feeling and being nervous that we might not make the quarter-finals.
“You only get three games in the group phase and all three opponents are very strong, so you really cannot afford to slip up.”
Portugal hosted the finals in 2004 eventually losing out to surprise winners Greece and reached the quarter-finals in Austria and Switzerland four years ago.
Captain Cristiano Ronaldo is confident that the Portuguese side can go all the way this year despite finishing behind Denmark in qualifying and requiring a play-off win over Bosnia and Herzegovina to make it through.
He told reporters at his pre-match press conference: “When we enter any competition, we do so with the intention of winning it. We know it will be very difficult, but maybe this will be our turn.
The Real Madrid winger, scored 60 goals last season, has yet to fully deliver in a major tournament and believes he and his teammates need to remain focused and concentrate on their own game if they are to get off to a good start in their opening game.
“Germany are very strong opponents and they have great players, but I think that Portugal are a team who can always play well against top opponents,” Ronaldo said.
“We are facing one of the best opponents, but we have to concentrate on our strengths and be organised and keep our concentration, then we will see what result comes out of it.”
Per Mertesacker is the only injury concern for Joachim Low after taking a knock in training.
Portugal coach Paulo Bento could be without Nani who’s been unable to train in recent days.
A stunning season at Real Madrid will see the midfielder firing on all cylinders heading into the tournament. His performances in the 2010 World Cup lit up South Africa and if he produces the same again he could lead Germany to the their first major international triumph in 16-years.
Scoring 60 times in a single season and winning the La Liga title just isn’t enough for the Real Madrid star. Ronaldo wants to add the European Championships trophy to his glittering collection. He’s yet to fully shine on the international tournament stage but after a remarkable campaign it would be foolish to back against Portugal going all the way.