Celtic now know they will face Cliftonville of Belfast in the first Champions League match of the new season, but manager Neil Lennon is still unsure just who will be in his squad.

The Parkhead boss has added Dutch under-21 defender Virgil van Dijk to his playing staff as the Celtic stars return to work and pre-season training.

But key midfielder Victor Wanyama is now all but certain to leave the Scottish champions, with Cardiff now in the hot seat to sign him despite Celtic agreeing a near $20 million deal with Premier League Southampton.

Wanyama’s agents reportedly began talks with Southampton on Tuesday as Celtic awaited bids from the likes of Everton, Cardiff City and Arsenal.

But his agents denied the reports and insisted they were awaiting permission to talk to Cardiff as Southampton’s offer wasn’t acceptable to the player.

“We are not in talks with Southampton and have not been since their final offer of terms, which was more than two weeks ago,” his agent Ivan Modia told Sky Sports.

“The news of the fee being agreed may just be coming out now but we see little sense in a fee being agreed if there is no reasonable prospect of the player’s terms being met.

“To suggest we are talking with Southampton is totally false, their offer was way below Victor’s expectations. There is no chance of him signing the deal on offer and, in fact, both Celtic and Southampton were informed of this some time ago.

“The player will not be forced into a corner to accept the Southampton deal, just because it is good for Celtic. Remember, he has been with the club for two years now -- without a pay rise -- and has given them wonderful service ever since he arrived.

“Added to this is the fact that by Celtic refusing him permission to join Queens Park Rangers last summer, Victor lost more than £1m in potential salary earnings, yet he just kept his mouth shut and continued to be a model professional.”

Modia confirmed interest in Wanyama from other clubs and said, “We know there is interest from elsewhere and Victor is obviously open to those prospects. He is currently back in Kenya and hopes that Celtic will adopt a more reasonable approach and take into account the service that he has given the club so far and the rest of these issues.

“Nobody at Celtic can question his attitude and he is hopeful he can leave on good terms with the club. He loves the club and its fans, he’s played his heart out for the jersey but he didn’t quite expect that it may end like this.”

The 21-year-old has spent just two seasons in Glasgow after his move from Belgian side Beerschot for just over $1 million in 2011.

One player definitely available to Lennon for the new season is the young Dutch defender van Dijk who has signed from FC Groningen in a deal worth up to $4 million.

A statement from Celtic read: “Celtic are delighted to announce that defender Virgil van Dijk has joined the club from FC Groningen.

“The Dutch Under-21 international has signed a four-year deal with the Scottish champions, and he becomes the latest player to join Neil Lennon’s squad during the close season following the arrival of striker Amido Balde from Portuguese side, Vitoria Guimaraes.”

Rated as one of the best young players in Holland, van Dijk added, “I’m a strong defender and I’m good in the air, but I also like to play football on the ground, and I hope that we’ll do even better than we did last season.”