BRENDAN Rodgers is regularly said to have a blind spot when it comes to central defenders but the case for the Celtic manager’s defence lies in the hulking 6ft5in form of Kristoffer Ajer. Even if the Norwegian was originally brought to the club by his countryman Ronny Deila.

Celtic have conceded so many bad goals in Europe in recent times – after the three goals from crosses which cost them against AEK Athens there was another against Suduva in midweek – that everyone involved must take their share of blame. But if anyone can hold their head high about their contribution this season it is surely Ajer.

Arriving in this country as a callow, willowy central midfielder, since moving to centre-half Norwegian has put on more than a stone-and-a-half of bulk under the watchful eye of the club’s physical trainers, and generally come to grips with what is required to play that position.

He is pushed off the ball no longer - by even the most physical Scottish striker - and appears to have added the weight with no diminution of his powers to cover the ground or bring the ball skilfully out from the back. And he is still only 20. No wonder Brendan Rodgers recently said rather cryptically that Ajer was his "two best central defenders".

“Of course we have conceded some goals that should have been prevented,” said Ajer. “We just haven’t been good enough at the decisive moments in our box and that’s something we need to improve.

“And of course, I’ve played almost all the games this season and been the part of conceding goals. It doesn’t matter what age you are, you’re in with the rest of the team and you have to take the blame too. But we are such a strong squad and we know that we can mistakes and concede goals. We will never start blaming each other. Everyone has his job to do. It’s not only one guy or two guys at fault. It’s shared. It’s important to look at it, work on it and hopefully not do it next time.”

The tallest kids at school aren’t always required to leap to win headers, or be the biggest leaders around. Fortunately Ajer takes his personal development seriously.

“I have always been a physical player but I added a lot of weight too - that was needed to play at centre-half,” he said. “I was 83kg when I came and now I am 93.5kg.

“I found out really quickly when I got moved to centre-half that that was needed. I have been working really hard with John Currie, our physical guy. He has been working really hard with me after training in the gym. They have put me on a really good programme and it was also good to go out to Kilmarnock and get that physical development there too. That was really important.

“You need to get used to strikers going up against you. There’s a fantastic physical side to the game in Scotland and that’s something young players need to learn about. I had to develop that but I feel I’m getting better at it.

“I had to start eating more but also training in the gym. It has been a good programme. I have been training a lot on my explosiveness. All the parts that are important in football. It’s taken two years but I think it’s been important to take that time. You could put the weight on a lot quicker but then miss out on something else."

From time to time these days, you may even see this mild-mannered Scandinavian digging out a colleague for something or other.

“When you’re playing you have a responsibility," he said. "Especially here at Celtic there is huge pressure in every single game. You have to be vocal and demanding of yourself. That’s something I feel I am also developing. I feel I have grown into that. I am learning from the experienced guys and they are vocal with me and accept that I will be vocal with them too. That’s how it needs to be in a professional environment.”

While Celtic are desperate to find a reliable partner for Ajer, this week of all weeks, that task at best remains a work progress. Jozo Simunovic left Lithuania with his right foot in a protective boot, while Dedryck Boyata’s status for the club’s three home matches this week – Hamilton today, Suduva on Thursday and Rangers next Sunday – remains shrouded in uncertainty. That is why a move for Aberdeen's Scott McKenna made such sense, perhaps to play on the left side of a back three.

Having apparently been priced out of that move, the transfer window in Scotland closes on Friday and there are no guarantees of getting anything over the line.

“If I am an English Premier League club, if it is a centre-half for example you are looking for, you are really not going to let go any of your top four centre-halves, because you can’t replace,” said Rodgers. “Unless there is anyone who is quite clearly out of the picture. Or one from another country. Certainly the English market will be tough I would say.

“There is a lot of work going on behind the scenes in order to identify and look at availability of players, but it is always about the affordability of that as well. To repeat, this was a window which should have been pretty straightforward for us. And thus far it hasn’t been. We have a period of time now to see what we can do and we hope to strengthen the squad.”

But the Northern Irishman's mantra is about the virtues of working with the players he does have at his disposal. Starting against Hamilton today, Rodgers insists that his team must stop giving gifts to the opposition.

“We have given too much encouragement to teams," he said. "Thursday night, we start well, get the goal. Our two games against Athens, we start great, get the goal, could go further in front then concede a cheap goal. There is no way to dress it up. You have to defend better, you have to take pride in it, and action it.”