Celtic manager Neil Lennon has said that Kieran Tierney left Celtic in order to take up a 'new challenge' at Arsenal.
The new signing joined the Gunners in a £25m deal on deadline day, bringing the end months of speculation over his future.
Tierney was joined by former Chelsea defender David Luiz as the new arrivals sealed their late moves in order to add depth to Unai Emery's defensive lineup ahead of the season opener against Newcastle on Sunday.
Celtic fans have taken to social media to show their displeasure at the player for moving away from Celtic Park, but the Hoops manager can see both sides of the argument.
"I can understand their point of view because they're Celtic fans and the only thing they see is Celtic. They may find it difficult to comprehend why he would want to leave Celtic," he said of the fans' reaction.
"But, what he's alluded to himself, he's had a great time here, probably achieved everything that he has wanted to achieve and he's just accepting a new challenge a professional challenge as well as a personal challenge in his life.
"It's understandable, it's going to hurt us because we're losing a very good player, but these things crop up now and again in football. All teams sell key players eventually and Kieran in no different in that regard."
Trippier is still recovering from injury, so will be unlikely to be able to make his debut against Newcastle.
