The most common mistakes that people make heading into the new season of fantasy football are mistakes of assumption.
One assumption concerns individual player trends. So many people assume that whatever happened last year, is exactly what will happen in the next. If someone has a down year, it is assumed that they will continue to decline into a miserable state of worthlessness. Likewise, if someone has a breakout 2007 it is assumed that 2008 will bring nothing but sunshine, roses, gumdrops and happiness for the player. Take a look at the preseason rankings from just one season ago. They are vastly different from what really happened. The same will be true of this year. Unexpected things happen. Don't laugh if someone drafts Steven Jackson over LaDainian Tomlinson, it could very well turn out to be the right move.
A good fantasy football player will look into the causes behind declines and spikes and realize that player performance can display the same unstable volatility as team performance. A player that exceeds expectations subsequently has his expectations raised, and is less likely to meet them the following year. A player who performs poorly, sees his expectations fall, and frequently surpasses those expectations as he returns to form the following season.
Another assumption that bites many fantasy geeks is to believe that teams never change. Frequently, identities are assigned to teams (for example: Baltimore and Chicago are defensive juggernauts with bad offenses, Indy is a passing team with poor defense, Denver always has a great running back, etc.). Unfortunately, those identities remain long after reality has changed. Baltimore and Chicago had poor defenses last year, Indy had one of the best defenses in the league, and Denver hasn't had any individual put together a good season running the ball since 2005.
Don't buy into the party line. Look at what each team has accomplished the previous season without bias. Use that as a starting point for what you can expect heading into the next season. That initial evaluation should change based on coaching, personnel, and schedule changes, but it's a start.
A third assumption that dovetails with the previous assumption is one that relates to the coaching staff. Don't assume that because a team has always done things a certain way, that a new coaching staff and front office makes no difference. When Kansas City hired small-ball, defensive-oriented Herm Edwards to replace the offensive-minded gunslinger coach Dick Vermeil, many savvy fantasy players saw the writing on the wall and hopped off the Trent Green and Larry Johnson bandwagons. A few years later, there is little left that would be mistaken for an impressive offense in KC.
Coaching changes always matter! This really can't be emphasized enough. It may not happen in one season, but eventually a coach will have the team running the way he wants it, regardless of what the team was good at prior to his arrival.
Another assumption that can really hurt you is to believe that you are unbiased. If you want to be successful in fantasy football you have to know how to separate the inner fan from your logic. If you are a fan of the Giants, Eagles, or Redskins, I know that you really, really want the Cowboys to fail. You want Romo to be a fluke, TO to OD on pills, and the team to crash and burn with a 3-13 record. That doesn't mean any of that is likely to happen. If you can't kill the inner homer, and separate your evaluation skills from what you want to see happen, you will perennially wind up with a team of players from your favorite team, nice guys that you like, and people you hope will be good. If that's the way you want to play fantasy football, so be it. Just don't hold on to any expectations that you will also be successful.
Another poor assumption is to believe that the more a player appears in highlights or commercials, the better he is. This sounds easy. I'm sure many of you are saying "Oh, come on! I know better than that." However, stamping out the influence of hype in your thought patterns is really quite difficult. You've been told so often that some players are good and that others are terrible, that you don't even realize that you no longer fight it. Let's play a game: Word association!
Reggie Bush. (public response: "He sucks!" Reality: could be quite productive with a healthy knee this year and no strong complement in the backfield taking away carries)
Darren McFadden. (public response: "The next Adrian Peterson!!!" to some and "He's an overhyped Rookie who's going to crash and burn!" to others. Reality: Maybe, maybe not. Rookies are next to impossible to predict)
Larry Johnson. (public response: "An easy top 5 pick!" Reality: He may have the talent, but with a lousy O-line, and an unimaginative offense he's far more Clark Kent than Superman. Be careful.)
One last assumption that has fantasy footballers in tears by the end of the season is to assume that every acquisition and draft pick made by a team is an improvement. Sometimes another team's trash...is trash. Pay attention to all of the moves made by a team in the offseason. Some get more play in the media than others. When you look at Cleveland's defense, you'll probably remember that they traded for DT Shaun Rodgers to shore up that defense. What you may have missed is that they shipped their best cornerback, Leigh Bodden, to Detroit as part of that deal. Don't just assume that their defense will be better without weighing the impact of all of their moves, not just the glamorous ones.
To help you (and myself) combat these assumptions, I will be going through the league, team by team, and compiling the significant changes in personnel and coaching on each roster and analyzing how those moves impact the team, and give an honest assessment of the fantasy outlook at each position.