Ryan Gauld mate. Now 22 and spent last season on loan at some gash Portugese team.
Celtic were linked with him when he played in Scotland as well. The few times I saw him play for Dundee United, it was obvious he was a skilful player, but he wasn't always in the Dundee United team, and if you're not a guaranteed first team player for Dundee United, you're hardly ready to be a Celtic first teamer.
I tend to be a tad cynical when it comes to young players who are going to be the next big thing, and like to wait until I've seen them before I decide if they're as good as the press say they are. I wasn't surprised when he didn't make it at Sporting. Tierney has been an established Celtic player for a few years now. In my opinion, he'll be a star when he eventually goes to the Premiership.
It can work the other way as well, and Daryl Murphy was a complete disaster for Celtic, and for such a big man you'd have struggled to slip a Daily Record under his feet when he jumped for the ball. He left us, and tore up the Championship, and I believe he's now in the EPL, with Newcastle, which totally astonishes me.
When Martyn Waghorn was at Sevco he was a joke figure amongst Celtic fans, but I read somewhere that he's done really well at Ipswich, though I haven't actually seen him play since he left Scotland. Graham Dorrans played for WBA in the Premiership, but has been pretty poor for Rangers and hasn't kicked a ball whenever he's played against Celtic.