The Chelsea boss believes the loss of the captain against Germany could be crucial for the hosts and has backed Dante as the correct choice to replace him in the semi-finals
The Selecao captain scored the opening goal of the quarter-final win over Colombia but picked up a yellow card for blocking goalkeeper David Ospina's kick in the second half, ruling him out of the semi-final clash with Germany.
Star forward Neymar has also been ruled out for the remainder of the World Cup after suffering a broken vertebrae in the closing minutes of Friday's match, but Mourinho believes the Paris Saint-Germain defender could prove the bigger loss in the last four.
"Brazil need Neymar because he is a player who can win one-on-one situations, cause imbalance in opponents, score goals and is fantastic with set-pieces," Mourinho was quoted as saying by Marca.
"But I would say that, probably, Thiago Silva is as or more important than Neymar at this moment.
"His will be an important absence because Brazil are based on that defensive structure. It's how Thiago gives great stability to the team."
Napoli utility man Henrique replaced the injured Neymar late on against Colombia and slotted into defence, but Mourinho believes Dante would be the correct choice to partner David Luiz in Thiago Silva's absence due to his knowledge of Germany's Bundesliga stars.
"Of course they have Henrique and Dante as options to play. Against Colombia Henrique was chosen, but Dante plays in Germany and knows a lot of the players he will face, both those of Bayern and the Bundesliga," the Portguese added.
"For that reason, perhaps, Dante will be chosen."