Moriba did not feature for the Blaugrana in pre-season and also missed the start of the La Liga campaign against Real Sociedad last week due to a contract stand-off with the Barcelona hierarchy.
The 18-year-old’s contract with Barcelona expires next summer and he has been linked with moves to Manchester City, Liverpool and RB Leipzig.
It has been reported that Moriba’s reluctance in agreeing a new deal at the Camp Nou is because he and his representatives are demanding more money; something Barcelona have reneged on due to their current financial predicaments that have seen them let go of Lionel Messi.
Koeman has been left disappointed with the situation and has warned Moriba to place his career first at this stage.
"I talked with Ilaix two or three weeks ago. His situation, for me, is horrible," the Dutchman said on Friday ahead of Barcelona’s trip to Athletic Bilbao.
"He's young. He's 18, he had the opportunity to play for Barca and he's the future of the club. And he doesn't play, he's not with us.
"At 18, the most important thing is to play, not money. But Ilaix and his people think differently. I'm disappointed with that because I believe more in football than in contracts.
"Money at 18 cannot be the most important thing."
Moriba made his debut for Barcelona in January this year and went on to feature 18 times across all competitions, recording one goal and two assists in La Liga.
