I disagree with this. Defensive awareness, interceptions, marking etc is a skill of it's own. You cannot expect a midfielder to play fullback and do a good job at defending, the most you can expect is hard work. Marking is not easy, and it's not the only concern you have when playing football. Especially if you're a wingback and expected to also get up the pitch on counter attacks. Marking random people on a crappy pitch in a sunday league is not the same thing as marking PL players. Ritchie is not a fullback, he's a midfielder. He may be past it now and should probably be moved on, but he was good in his prime before being forced back to LWB.
