To be clear: Nobody's done a great job of doing that, thus far. With the Saints' patchwork defense, average running game and inconsistent performances from most of their wide receivers, it's been up to Jimmy Graham and Sproles to really carry the offense. Unless you count Drew Brees, but man, I'm tired of talking about Brees.
Stopping those guys is going to fall to the linebackers. Curtis Lofton is strong as an ox and twice as powerful, but he's not quick enough to keep up with Sproles. Stephen Nicholas comes closer to it and will undoubtedly draw Tiny Darren a few times, but it's Sean Weatherspoon who is best-equipped to deal with him.
'Spoon has developed at an alarming rate. While he still struggles with his tackling at times, he's almost always around the ball. His combination of strength and speed make him arguably the team's best coverage asset at linebacker, even if there are foibles he has to overcome. For that reason, he's likely to be after Sproles and probably Graham quite often.
Keep a close eye on 'Spoon. His performance in coverage is likely to be a game-changer.