About the play: The Vikings are known for throwing the ball, but the running game can set them apart. They have a physical offensive line and a back in Robert Smith who hits the hole very hard and quickly.

This play is a good change-up to the more slow-developing run plays. It hits so quickly that the defense has little time to react, which lets Smith get into the secondary very quickly -- as long as there's proper and quick execution.

Smith will hit the play right off the center's right cheek. Quarterback Jeff George will take a big step away from center and hand underneath to Smith, who will run off the center/right guard trap block. The man being trap-blocked is the nose guard. The right guard will go first and side swipe the nose tackle, who is anticipating the center's block. However, the center is coming in behind the right guard and helping on the end. The fullback will lead through the hole on the middle linebacker and give Smith a chance to cut either way.

Keys: The big key is the right guard's ability to move the nose tackle. His trap block must move the nose so Smith has vision to the hole.

Critical players: It is critical that the backside left guard and left tackle do not let their people cross their face. They must also control the weakside linebacker so he can't chase down Smith. It is also paramount that the fullback get on the middle linebacker and move him.

When to expect it: The Vikings have to make "20 trap" go so they can take pressure off the pass game. They must run this two to four times against the Chiefs, who have an aggressive, physical defense.