The 18-year-old is one of Scotland's hottest properties now
The 18-year-old has been superb for the Hoops in his breakthrough season, starting 35 games in all competitions since breaking into the side last November by displacing Emilio Izaguirre, reducing him to a bit-part role more or less.
By virtue of his excellent emergence, Tierney was named as Scotland's Young Player of the Year, and earned his debut for the Scottish national team earlier this year.
But Deila says that the youngster did have a few creases to iron out in order to reach the status that he currently holds in Scottish football, and backs him to be a "great Celtic player" in the years to come.
“When he first came into the team he struggled a little bit with challenges in the air but you can see now that he is getting stronger there," he said via the Glasgow Evening Times.
"Technically he can still be better but with experience he will be a great Celtic player.”
Giving Tierney his debut may be one aspect which Deila - who will leave the Hoops this summer - will reflect on with pride. Of course, he won two Scottish Premiership titles, but he has not been a roaring success in Glasgow, though Tierney certainly might be.