Southampton manager Russell Martin is unlikely to have many complaints about the quality of his squad, but that does not mean to say they will not be targeting one or two additions this January transfer window. Southampton have already been linked with Hearts striker Lawrence Shankland given the long-term injury to Ross Stewart and the uncertain future of Che Adams, but they are now linked with a 19-year-old midfielder who is yet to make his first-team debut. Ussumane Djalo is the player in question, with the Porto midfielder having played solely for the club’s ‘B’ team in the Portuguese secon…