Of all the skilled positions, running backs can often benefit the most by playing defenses who struggle against the run.
Let's look at three players who have favorable matchups in Week 2 and must be started in any type of fantasy league.
Alfred Morris, Washington Redskins
Alfred Morris was a pleasant surprise for fantasy owners who started the Redskins running back against the New Orleans Saints in Week 1.
Morris rushed for 96 yards with two touchdowns on 28 carries in his team's win against the Saints and will certainly benefit from the passing game doing well because of Robert Griffin III's impressive play at quarterback.
Against the St. Louis Rams in Week 2, expect Morris to have another strong game. The Rams allowed 83 rushing yards to the Detroit Lions on Sunday, who are a team with an average running game.
Week 2 Projection: 105 rush yards, 2 TD
Jamaal Charles, Kansas City Chiefs
Charles played very well in his first regular season game since tearing his ACL in Week 1 of the 2011 season.
He rushed for 87 yards on 16 carries (impressive 5.4 yards per carry average) and probably would have touched the ball more if the Chiefs weren't trailing most of the game and had to throw the ball often.
Charles will play against the Buffalo Bills in Week 2, whose defense was destroyed by the New York Jets on Sunday.
Jets running back Shonn Greene ran for 94 yards a touchdown, and there's no reason why Charles cannot do the same, or have an even better performance.
Week 2 Projection: 140 total yards, 1 TD
Adrian Peterson, Minnesota Vikings
Peterson's first game back after he tore his ACL on Christmas Eve was a fine performance in a huge Vikings win against the Jacksonville Jaguars.
Against an underrated Jaguars defense, Peterson carried the ball 17 times for 84 yards and scored two touchdowns.
Against the Indianapolis Colts, who don't defend the run particularly well, Peterson should rush for 100 yards in Week 2.
The Colts allowed 114 yards and three touchdowns on the ground against the Bears, so there's no reason why Peterson can't have a phenomenal game against Indianapolis next week.
Week 2 Projection: 125 yards, 2 TDs