He really isn't, he's improved from being the worst full back in the division - his performance on Saturday was appalling and that's what he used to turn in eight times out of ten, minimum - to one that most of the time looks just about competent and suitable for a mid-table, nothing team. I'd liken it to Fellaini's "improvement" for Man Utd from where he was in his first season. Nothing like the level that either team should be aspiring to, even if it is a lot better than the eyewatering shit that came before it.
Of course we have signed much better players to ensure that we don't have to play him, we just keep doing it regardless.