The Kansas City Chiefs started the season hot, with two impressive looking wins over the New York Jets and the Oakland Raiders. Their offense was exceptionally balanced and the defense was dominant. Then, all of a sudden, the wheels seemed to fall off and they dropped two games to Denver and Philadelphia. The Broncos completely dominated the Chiefs 30-10 with a good running game and a defense that shut down the Chiefs' running game and pressured QB Trent Green. The Eagles defeated the Chiefs with a great comeback as they were able to get pressure on Green and force him into some mistakes late in the game.
The common denominator in those two losses is that left tackle Willie Roaf didn't play in either game because of an injury. Because of the serious talent on the Chiefs' offensive line with left guard Brian Waters (Pro Bowler last season) and right guard Will Shields (10 Pro Bowls) leading the way in Roaf's absence, some people thought the Chiefs would be able to get by. Those people don't understand the importance of the left tackle to the offensive line.
I played left guard at a high level for 12 seasons and made it to a Pro Bowl and I know that even in my prime, I couldn't play the left tackle position. After the quarterback position, left tackle is the toughest position on the field to play and especially in the Chiefs' case.