The World Cup winner says the 25-year-old could miss out on a place in Joachim Low's starting side in Brazil having endured a difficult debut season at Arsenal
The 25-year-old, who joined Arsenal from Real Madrid in a club-record €50 million deal, has faced criticism over his form following a missed penalty against Bayern Munich in the Champions League in February.
Matthaus – who was a key part of Germany's World Cup triumph in 1990 – believes Ozil could subsequently lose his place in Joachim Low's starting side, especially given the wealth of talent available.
"Ozil has no guaranteed place in the starting lineup," he told Kicker. "Especially in his position as we have a lot of quality. First of all, he must prevail there. He could be the loser if you look at the way Low let his team play recently.
"But you always expect more from him than from other players. I don't think Ozil is untouchable."
Low has already confirmed he will wait to see which of his players adapts best to the Brazilian climate before deciding on his starting XI to face Portugal on June 16.