The Costa Rica international, who has been struggling for first-team appearances this season, had a spell with Gent and was quoted this week as saying he would consider a return to Belgium ahead of the World Cup.
|6/1||Bryan Ruiz is 6/1 with Coral to be Fulham's top scorer this season|
"He is on our list. Ruiz is a good player, but not our first choice," he told Het Laatste Nieuws.
"I have a plan A, a plan B and a plan C and I'm happy my plan A hasn't been leaked yet.
"Of course we know Ruiz's qualities. We have made a list of players who will go to the World Cup, but aren't playing regularly. Ruiz is on it, but so are others."
Van Holsbeeck hopes the offer of first-team football will lure Belgium international Defour back to his homeland.
He added: "Anderlecht will be a good option for him. Let's say he joins Fulham, then he will have to settle again.
"At Anderlecht he will be the star. If he wants to be sure of his place in the Belgian World Cup squad, then we are a perfect option. Steven is an intelligent guy. I think he knows this."