A lot of revisionism tends to be said about Lucas. Until 14/15 for instance he was still making an incredible positive difference in our league results, and indeed he was the key to our good run that ended with a home loss to the Mancs. I still remember Carragher making this analysis showing how Lucas had played in that run of games and how we got absolutely destroyed the only game (Mancs away) he had missed.
So, no, I don't buy into the 'not a very good player since his injury' bit. He clearly has been a good player for Liverpool, one that every manager that's been with us seemed to trust. Now it just so happens that we have a markedly different style where he can't really play as a DM anymore. In fact, we don't even play with a DM. That doesn't make Lucas a bad player at all.
As a CB I think he gets more exposed than he would have as a DM in, say, a Rodgers's side. But, again, this doesn't make him a bad player, or, as some say, the embodiment of LFC's mediocrity. I'm not sure how long the Lucas as a CB experiment is gonna go on for, and I do think ideally we shouldn't be having to improvise players. If he's not to play as a DM for us, then sadly I don't see too much future for him here. But until he goes he will always be a decent player, and even as a CB he can put a shift in and deliver in the right system.