http://news.soxprospects.com/2017/04/scouting-scratch-rafael-devers.html
A lot of the questions about Devers center around his defense, but these concerns have evolved not from actual concerns about his ability to field but rather questions when he signed about whether he would grow out of third base, necessitating a move to first. If you see him play the field, it’s clear that there is no reason to discuss a move off third base at this point. Perhaps, he could eventually become too big, similar to what happened to Miguel Cabrera, but his skills should allow him to stick at third for the foreseeable future. Devers is a below-average runner already and not the most athletic player, but he shows off surprising range and agility moving both laterally and charging the ball.
Over the four games scouted, Devers made one error charging a ball that he stabbed at to the side, rather than fielding out in front, but he also made several very good plays. He has soft hands and his footwork is surprisingly good. He made one very nice play in the season opener ranging to his left to cut off a ball in the hole between third and short, and he made two others that same day charging slow rollers, fielding them with his glove and making smooth transfers to his throwing hand and then strong, accurate throws to first base. Devers has plenty of arm for third with it grading as plus currently. Devers is unlikely to be a Gold Glove candidate, but he also won’t be a butcher and should develop into at least an average third baseman, an outcome the Red Sox will happily accept given his offensive potential.