He admitted: “It is so important for me that we have players such as Callum and Kieran in the team, for lots of reasons.
“They know the city, they know the culture, they know what it means to pull on the shirt and what they have to do to keep it.
“I always think that players who come from families who supported the club are willing to sweat blood for it – they give everything.
“But it is more than just that. I think it great for our academy players to look and see that it is possible to play here.
“You can come to Celtic and you can make it to the first team – it is important to see the heroes every day. That is the message we want to put into the academy, that you can make it here.
“That is why guys such as Charlie Mulgrew and Scott Brown are so important, too. Charlie came close, went away and came back and these guys are Mr Celtic now.
“Scott is working with some of our youth players in a coaching environment and keeping that strong Scottish spine is something we always want to do at this club.
“Of course, we will always look to do business in the transfer market because we want to be at top club.
“We see ourselves as a Champions League club and it is about building a team with a mixture of youth and experience that can take us to that level now.”
Tierney,18, has taken over at left-back from Emilio Izaguirre in recent months while 22-year-old McGregor returned to the midfield after injuries to the likes of Mulgrew, Brown and Kris Commons.
Deila said: “He has taken his chance. He has worked hard, he is playing well and it is up to him now to stay there.
“We are pleased with him. He can create and his confidence is good at the minute.
The champions face two massive games within the next week with a League Cup semi-final against Ross County at Hampden on Sunday which is followed by a midweek trip to Pittodrie to take on Aberdeen, six points adrift at the top of the Premiership.
“It is something that you can’t do anything about, but everyone saw the game and saw what it happened and it just shows how tough it is.
“These games that are coming up now are so important and it is so important that we go into them in the right frame of mind.
“Ross County on Sunday at Hampden gives us the chance to move forward and put ourselves in a final which is always a big motivation.”