Dutch great Ruud Gullit says Frenkie de Jong must improve for Barcelona.

The 22-year-old cost the Catalan club 75 million euros when they bought him from Ajax last summer.

"There are lots of stories about how great Frenkie is playing at Barcelona and I have my doubts in that respect," Gullit told Voetbal Primeur.

"I think that, in reality, he's not playing so well and that he can do a lot better.

"I'm saying this because I know he can do better. Frenkie has to play better.

"I still have confidence in him because it's great to see that he's connected, but I see what is happening."