He's definitely improving but some of the comments in here are OTT, I would say he had a solid game apart from one lapse in concentration. Having just watched the game back I feel like we take a lot of Smalling's aerial wins/clearances (and his general physicality) for granted - near enough every set piece / corner is cleared by him, Lindelof just doesn't have this in his game.
Ronaldo was fairly quiet last night and at OT and I think that's largely down to Smalling winning the physical battle, and Lindelof covered a few times as well to give credit.
The goal is obviously world class but Lindelof's positioning was wrong to begin with (too deep), he then loses sight of Ronaldo and before he knows it he is chasing him. Not a massive error but as others have said in this thread, I would have expected other (more physical) defenders to have dealt with it better, he needs to be more physical - had he kept Ronaldo in touching distance he could have disturbed his run but Ronaldo ran through completely unchallenged. It's almost as if Ronaldo knew he wasn't having much joy vs Smalling so pulled onto Lindelof and got his goal.
The most promising part of his performance last night for me was there was a couple of times he was bringing the ball out of the back and finding the right pass, something he had a reputation for when we signed him but up until recently we haven't seen too much of it. Really like him as he comes across very well and there are have definitely been improvement but there is still a long way to go IMO.