The Dutch defender was missing from the Hoops' 1-1 Premiership draw with Dundee at Dens Park amid speculation linking him with several clubs such as Southampton, Newcastle and Sunderland.
Celtic manager Deila was speaking after watching substitute Leigh Griffiths level a first-minute header from Dundee defender James McPake for a share of the spoils in what was another indifferent performance by the champions.
Deila, who expects to sign 24-year-old Serbian striker Stefan Scepovic from Sporting Gijon, revealed a chat with Van Dijk ended with the player being informed he is going nowhere this summer.
"He is a very important player for us and we have told him that there is no chance he is going to leave," Deila said.
'He is too important to us, so there is no chance we will let him go during this window. We couldn't replace him.
"We talked about it. He wishes to get to a new stage. He is a young player and a young man and he will get many chances in his career.
"But now we need him here and he knows that and that is how it is going to be.
"His girlfriend is also pregnant and due soon. So he hasn't had the right focus, he wouldn't have been 100 per cent today - that is why he didn't play."
Asked how Van Dijk took the news, Deila said: "I think it's no problem. But he needs a couple of days to get this out of his system, get thinking positively again."
Griffiths, who replaced Jo Inge Berget just before the break, has been linked with a move to Hibernian but Deila also put an end to that speculation.
"Leigh Griffiths is going to stay as well," he said.
Deila refused to comment when asked about a move for Dundee United midfielder Stuart Armstrong.
However, on Scepovic, he put the delay down to paperwork and said: "We hope that that can be arranged.
"He wants to play for Celtic. That's a good start. The process is ongoing."
Celtic goalkeeper Craig Gordon will be delighted to have Van Dijk in front of him following the international break and is confident the Dutchman will be committed to the cause.
"When he's crossed the white line he's done everything he can to help us win games," Gordon said.
"Virgil is a massive player for us. He's excellent and has been a fantastic player this season so it will be great if the club holds on to him."
Dundee are unbeaten in five Premiership games but manager Paul Hartley was disappointed his side could not take all three points.
The former Celtic midfielder said: "I thought we created the better chances and had good situations, especially in the second half when the boy (Martin Boyle) is through on goal a couple of times.
"He had an easy pass for a tap-in - but he's got a split-second decision to make.
"I thought it was a great game of football and I thought we were excellent."
McPake, who headed in a Philip Roberts corner, smiled when he realised he had said "I am happy to be sitting here disappointed" while ruing the appearance of former Livingston and Hibs team-mate Griffiths, who scored with the help of a deflected drive.
"I knew he would score when he came on," McPake said.
"I spoke to somebody last week and I said I hope he isn't even stripped.
"He hits the ball so cleanly and if there is somebody two yards in front of him there is a chance it will go in.
"Maybe if he hadn't have come on we would be sitting here with the three points."