Rojo is a very versatile defender that can play multiple positions. He had a very solid World Cup playing for Argentina. Van Gaal is moving to a new formation this year, so Man U needs flexible players that can fit his system. Plus, their wonder-kid signing (Luke Shaw) is still injured and the Swansea game exposed their defensive frailty, so another quality body was sorely needed. Unfortunately, Man U's once very formidable back line (Vidic, Ferdinand, Evra, et al) got old around the same time, and the club kept them around far too long. I honestly think that the aging squad was one of the reasons Sir Alex got out when he did...he didn't want to face a major rebuilding task.