Mueller, who scored four goals in the tournament, was suspended after picking up his second yellow card in the quarterfinal win over Argentina.
"It would have been different with him," Germany coach Joachim Loew said. "This can always happen when a player is suspended. In the last games he has been a very dangerous player and scored goals. He is a player that scores a lot and gets behind defenses. He hurts opponents.
"He would've suited our style of play very well against Spain."
Mueller is coming off his first Bundesliga season, but the 20-year-old versatile Bayern Munich forward has been one of Germany's most effective players. His ability to produce the unexpected, his clinical finishing and timely passing had made Mueller hard to read for opposition defenses.
The absence of Mueller was only one of the factors in Germany's defeat.
Loew was unable to find a winning strategy similar to the game plans that sank England and Argentina, which Germany beat 4-1 and 4-0 respectively.
"Our plan was to win possession quickly and then try to keep it, to pass the ball around," striker Miroslav Klose said. "But it didn't work. They passed the ball very well, they made us work very hard in the defense. When we finally won the ball, we were too tired to move quickly forward.
"They have been playing together for several years, they are very cohesive, their moves come automatically. They were simply the better team," Klose said.
Klose never got enough supply of useful balls and remains one goal shy of Ronaldo's 15-goal World Cup record.
"I guess I'll never win the World Cup title," said Klose, who lost the 2002 final with Germany against Brazil and was on the losing side against Italy at the 2006 World Cup in Italy. At 32, Klose is the veteran on the team and probably in his last World Cup.
The Germans were unable to force Spain into making mistakes, which is what Loew had said would be the way to beat the European champions. Spain beat Germany 1-0 in the European Championship final two years ago.
"The disappointment is very big," captain Philipp Lahm said. "We had a lot as our goal and we didn't succeed. We were not brave enough in the first half to go forward more. We didn't allow too much in the back but we had to use our few chances."
Goalkeeper Manuel Neuer also said his team had too much respect for Spain.
"We created few chances. They didn't allow much and created many chances. We lacked a bit of courage. In previous games, we usually scored before halftime and that had always increased our confidence," Neuer said.
Loew congratulated the Spanish team and predicted that it would beat the Netherlands in the final.
"They move the ball well and we couldn't play the way we like to play. They had a certain dominance," Loew said. "They won Euro 2008 in a great manner. They've won all the big games in the last year, it's a very good team that has played together now for two or three years."
Loew will now have to motivate his players for the third-place match against Uruguay in Port Elizabeth on Saturday.
Germany arrived in South Africa with its second youngest team ever and achieved its declared goal of reaching the semifinals. Clearly, the players wanted more, but the team certainly has a bright future.
With an average age of under 25, this generation will be peaking just at the time for the 2012 European Championship and the 2014 World Cup in Brazil.
