The Holland Under 21 international hardly featured under Alex McLeish at St Andrews after being brought to the club by Steve Bruce.
The 24 year old has spoken of his frustration at not playing regularly and he could decide to move on in search of regular first-team action.
De Ridder's agent Mino Raiola has confirmed clubs from England and elsewhere around Europe are chasing the former Ajax ace.
"There is some interest in Daniel as he is a quality player," Raiola told skysports.com.
"There are clubs in England and abroad who are looking at him.
"We will try and resolve something with Birmingham to suit everyone."