RONNY DELIA is confident that Virgil Van Dijk wants to be a Celtic player beyond the January transfer window and claimed that the Dutch centre-back was on course to be a "world class player".

The Celtic manager was forced to leave Van Dijk out of his side after the summer transfer window closed, and said that the 23-year-old had been affected by failing to secure a move.

Yet, with suitors from the Barclays Premier League circling the talented defender, Deila said: "He's very happy. I have talked to him. And we are very happy to keep him as well. He's a top player."

The Norwegian manager sensed no "desperation" from Van Dijk to leave the club, saying the defender had learned from the aftermath of the last transfer window when he was dropped for a match against Dundee because his mindset was not right.

"I think he has learned a lot from this; it's not the first time a player has been affected," said Delia. " Others have been through these things as well. Stefan Johansen was the same. He came from the Euro finals with Norway two years ago and played so badly for Stromsgodset. I have never seen him so bad because his mind was somewhere else."

But the manager believes Van Dijk is fully committed to the club despite reported interest from Arsenal, West Bromwich Albion, Newcastle United and Sunderland.

"He's worth a lot of money," said Delia of the player bought for £2.6m from Groningen in 2013 but valued at up to four times that now. "I am very calm. Virgil is enjoying his football, playing well and, when I speak with him, he's happy here. That's positive. He is such an important player for us."

Deila believes that Van Dijk can use Celtic as a platform to reach the very top of the game. "He can become a world class player. He is a very good player now but he can be a world-class player," said Deila. He said the next move for the defender would be crucial, claiming he needed to find a club that both suited his talents and that "really wants him".

"That is very important for every player. It is not just about money. If a club buys you for a lot of money they really want you. If they buy you cheap, they maybe think 'Okay, I can take a chance on him."

Deila, too, says that Van Dijk is still developing. "His stats are good. Offensive stats too: scoring goals. He's getting better in defence, making fewer and fewer mistakes. He is sharper, quicker."

Typically, though, Deila is demanding more. "The next thing for him is to become a leader. We need that leader in defence who controls things. He's starting to do that but there are still a lot things to work on."

The intention is that these flaws are ironed out in the early months of 2015. Celtic will meet Internazionale in the last 32 of the Europa League in February and Deila concedes this is a "good opportunity" for a player who seems destined to leave the club eventually, if not in this window.

"Teams now will not see you in one game and then buy you; that's over," said the Celtic manager. "They see you 10 or 15 times and you need consistency. Your levels have to be very high especially in defence because they need people they can rely on. That's something I think he has done better now than earlier in the season.