I think it’s more that he seems to ease up too early before he’s actually won the race with the opponents, not that he doesn’t have the pace. I've seen him make up a lot of ground when he gets caught out so he definitely has pace. He has to be more aggressive and determined in his defending, he is prone to losing focus before the danger has been dealt with.
He simply needs to use his brain more, the best defenders are relaxed and ruthless at the same time. Too often Davinson either panics and rushes out or relaxes so much that he doesn't actually defend when he's in a good position. The penalty he conceded against Woolwich is a perfect example, it should be impossible to concede a foul in that situation as he was in the right position and anticipated the danger, but somehow he did. He needs to add that focus to his game and he can be world class. He has all the tools at his disposal.