“We want quality players who can help us. We won’t just take a player who will sit on the bench, we want a player who can change a game,” said manager Erol Bulut.
“I hope I will get one in but until now we haven’t been able to manage it. What clubs are asking, what players are asking with their wages, is difficult.
“[Simic] is a club signing for the future. He will have a loan to Kortrijk but we still have a little bit of time to get a player in, I hope. But it’s not easy to bring only one in… it has to be the right person.”
Cardiff have now signed eight players so far this summer, with striker Wilfried Kanga and wingers Chris Willock and Anwar El Ghazi bolstering their attacking options.
But with striker Kion Etete and winger Isaak Davies both injured, Bulut was keen to add to his squad.
Simic, who scored six goals from 34 appearances in all competitions for Red Bull Salzburg last season, has been earmarked for a first-team role at Cardiff next year.
Other Cardiff players have spent time on loan at Kortrijk recently, including Davies and defender Ryotaro Tsunoda in the 2023-24 campaign.