Khedira joined the Spanish giants from Stuttgart in the summer of 2010 and has since established himself as a key player for Los Blancos.
The Germany international is a regular holding midfielder alongside Xabi Alonso in Mourinho's lineup, while Fabio Coentrao features in central midfield and at left-back.
However, criticisms were levelled at both players last season despite Madrid winning La Liga, and Mourinho has now slammed those critics.
"I cannot understand why Khedira and Coentrao are criticised all the time in Spain," the Portuguese told Spox.
"This is because the media are always looking to write something negative. I currently do not know any other player who is better than Sami in his position."
Madrid are currently on a pre-season tour of the USA.