#4 Emerson Palmieri

After surprisingly not signing a left wing-back during last summer's transfer window - leaving Marcos Alonso without competition - Chelsea signed AS Roma's Emerson Palmeri in January. The deal was evidently not a convincing one as for the past year, the Brazilian left-back had rarely played any competitive football, having been sidelined with a serious ACL injury.
However during the previous year, Emerson had become a favourite with Roma supporters. Fans saw him as one of the league's best in his position, although Antonio Conte hardly granted him any opportunities to break into the side either. Presumably to avoid tension between himself and Alonso, an established starter, though the player did impress when selected during the Spaniard's own three-match suspension.
Possessing a good burst of pace, the ability to overlap his winger and cross the ball into dangerous areas with quality, it's clear that Sarri will expect him to compete with Alonso for the starting left-back berth.