Why it didn't work for Shane Duffy at Celtic - 67 Hail Hail

On paper, Brighton and Ireland defender Shane Duffy could've been a great signing for Celtic. So why didn't it work out for him?

Why it didn't work for Shane Duffy at Celtic - 67 Hail Hail
On paper, Brighton and Ireland defender Shane Duffy could've been a great signing for Celtic. So why didn't it work out for him?