That's according to former Arsenal player Emmanuel Petit.
The left-back is playing out his final few months as a Gunners player before he makes the move north of the border to his boyhood heroes, where it all began.
Brendan Rodgers secured the services of KT on a pre-contract earlier this year. He will return to the Scottish Premiership champions when his current deal in north London expires.
Petit is a fan of the Scotland international, however, he reckons there's been one major aspect missing to his time at Arsenal.
He told [PokerFirma](https://www.pokerfirma.com/): "Whatever people will say about Kieran Tierney, I think he’s been really unlucky with injuries and, whether or not you think his transfer to Arsenal was a success or not, he’s grown as a footballer.
"He’s gained some incredible experiences that will only benefit Celtic and his teammates.
"He was a key player for Arsenal, and then he got injured. They spoke of him as a future captain at one point.
"He lost his spot, and then he and the courage to go and try something different and went and played in La Liga for a season with Real Sociedad.
"Celtic will be getting a better player back than the one they sold, it’s never been a question of ability, it’s always fitness.
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"Tierney lost his spot in the first 11, he came back, and they moved on, they signed Zinchenko to play as inverted fullback.
"I presume that when you lose that confidence from the manager, when you are not considered as a top player or a first choice, then you lose your confidence a bit and I can understand that sometimes a player wants to feel at home, to feel loved.
"This is why I think that going back to his boyhood club Celtic, will be a good choice for him.
"He’s going back to where he came from to try to rebuild himself. It’s very important for a player to feel desired and for a player to contribute. He will be able to do that at Celtic."