Goodness me. I am going to have to go and study him harder, looks like. The more specific people can be in their criticism of him, the more helpful it would be to me.The best description I've seen of Tierney is that he's an elite Sunday league style player, full blooded but very inefficient.
On a slightly different note, I was watching an interview AOX did, and he said he could not understand how someone (Andy Robertson) who was so outstandingly bad in a rondo could be so effective in a match. What I have noticed about Robertson is that his touch is dodgy, and he doesn't strike me as a good passer of the ball. What you get is 90 mins of hard running from him, he will kick anything that moves, and he puts in some good crosses (or used to). What do you think?