The young Dutchman is no longer needed at Inter after just one season, and a return to the Eredivisie looms as the Enschede side look to replace Luuk de Jong
The Eredivisie side are in the market for a new attacker due to the imminent departure of Luuk de Jong to Borussia Monchengladbach, and the Tukkers see the 19-year-old as the ideal replacement.
Castaignos is a product of the Feyenoord youth academy, but left the Rotterdam giants for Inter in the summer of 2011.
However, he failed to make an impact at the Nerazzurri due to the stiff competition for places, and is therefore expected to be on the move again this summer.
The striker's current contract with Inter runs until June 2016, but an offer in the region of €5 million could be enough to entice him from the Giuseppe Meazza side.
Castaignos has also been linked with Sporting Lisbon, as well as a number of Premier League sides, but he reportedly prefers a return to his native country in order to relaunch his career.