He can't guard anybody except guys like Dontae Jones who have no offensive game.
He is the worst pick and roll defender on the roster. He doesnt even want to guard guys one on one cause he knows he cant. You constantly see him shade or open his body up while defending one on one, basically just conceding that he's going to need help from a teammate.
On the pick and roll, he never fights over the top. He gambles constantly when he off the ball leaving other in precarious positions.
I'm as big of a Rudy fan as anybody, but this guy gets such a pass from the fanbase. He's a huge liability on the defensive end.