Carvajal for defensive purposes. Lahm isn't the fastest anymore, and despite being a great clean tackler, Carvajal has that extra sort of physical aggression and the pace combined to ruin the day of fast wingers. But I think bigger teams that dominate the game will always find greater use in players such as Lahm who control play and make those fantastic passes. Those playmaking fullbacks look a dying breed, most fullbacks running around nowadays are either wingers or just fast, physical defender-hybrids.