Aberdeen last night knocked back a £3.5m offer from Celtic for Scotland defender Scott McKenna.

And it is believed that the Pittodrie have told the Parkhead side that the player is not for sale.

Derek McInnes is reluctant to sanction the sale of the defender with Aberdeen already knocking back bids this summer from Swansea, while Hull were also rebuffed in the January transfer window.

With nine days of the window remaining Celtic are keen on making additions to shore up their backline but Aberdeen are believed to have set a £6m price tag on the head of the 21-year-old who has a five-year deal with the Pittodrie side.

McKenna is currently sidelined with a hamstring injury that he sustained on the opening day of the season. However, the player has had a rapid rise over the last year and finished off last term by captaining Scotland against Mexico.

Celtic have been short of options at the back this term and had additional problems with Dedryck Boyata’s sage added to the mix.

it is believed that the Belgian defender will be handed a jersey to play against Suduva at some point on Thursday night’s Europa League qualifier in Lithuania.

The Belgian defender remains a target for Spanish side Seville, with the La Liga side confirming that Boyata is on their radar. Turkish side Fenerbahce have also been credited with an interest in the player.

The 27-year-old has been brought back in from the cold by Parkhead manager Brendan Rodgers after effectively downing tools when the club blocked an offer from Fulham.

Boyata claimed he was injured as Celtic flew to Athens last week as they went out of the UEFA Champions League at the third qualification round, something that was publicly refuted by Rodgers.

Boyata is fit after training with the Parkhead side and is expected to play against the Lithuanians tomorrow night.

However, it seems unlikely that the player will still be at Celtic when the window closes at the end of the month.

"Boyata is one of those players that we have been following for a long time,” said Sevilla’s sporting director Joaquin Caparros yesterday. “Defence is an area we need to reinforce. We must proceed calmly because there are many factors with a transfer that doesn’t just depend on ourselves.”

Olivier Ntcham is also continuing to attract interest. Celtic have maintained that the French under-21 internationalist is not for sale. There was interest in the midfielder from West Ham earlier this summer while reports in France yesterday claimed that Porto had tabled a bid of around £13.5m for the player.

Sources within Celtic dismissed that and it is believed that the player signed for £4.5m from Manchester City last term is one that they do not wish to cash on at this time.

Meanwhile, Celtic kid Calvin Miller has signed a one year contract extension with the club but is set to head out on loan in order to get some first-team experience.

“The manager is obviously confident in me,” said Miller. “He sees me long-term at the club and wants me to develop and that’s why he wants me to go out on loan.

“I feel like I need that myself. I need to be playing regularly as I need game-time and fitness and I’m sure as soon as I do that, I will become a better player.

“I’m training every day with the best players in Scotland. I’m learning every day playing against the best wingers and the most important thing for me is to keep working hard, express myself and be confident.

“Now I need to be playing week-in, week-out and that will make me improve as a player and be ready hopefully for next season.

Sunderland manager Jack Ross is also believed to be keen on taking Ryan Christie south of the border. Christie has not been able to make himself part of the first-team set up at Celtic. He had a successful loan spell with Aberdeen last year.