City are rallying around Silva after a slow start to his Premier League career.
"What we see of him in training we know he is a fine player," De Jong told city's website. "We have been very impressed. I played with him at Ajax in the Champions League I know how good he can be.
"He is a technically gifted player who just has to find his way in the Premier League. He can do wonderful things with the ball. He is a big part of the squad and a really important player for us. Salzburg will be a good step for him."