Speaking to Sky Sports, Giles said: "Arsenal approached us in the last two weeks about Christian regularly with Andrea Berta.
"I think it's fair to say it's more likely to happen than not. We have to go through the full process, tick all the boxes and then we'll see at the end of it.
"He's been a fantastic player [for] us, unbelievable. I'm actually happy for him with the opportunity at this stage, 31, at this stage of his career, to have an opportunity to go and try to win some trophies.
"It isn't done yet, but we're aware that if and when he does depart, we have a leadership void to try and fill. Also thinking about Ben Mee, who also left this summer, and Mark Flekken, who's an experienced goalkeeper. We're aware of the squad and the blend of experiences we have in the squad, and we'll look to cover it."