Chiefs lose All-Pro running back Charles to serious knee injury

One week after losing their star defender for the season, the Kansas City Chiefs lost their biggest offensive weapon in Week 2.

All-Pro running back Jamaal Charles(notes) left Kansas City's game against the Detroit Lions after suffering a left knee injury. The NFL's second-leading rusher in 2010 was breaking toward the sideline during a run in the first quarter of Sunday's game when he stuck out his left leg in an attempt to get past the first-down marker.

His knee buckled as he stepped on the sideline. Charles immediately fell to the turf, taking out the Lions mascot as he landed.

Charles didn't return to the game. Later Sunday, ESPN's Adam Schefter reported Charles will miss the season with a torn ACL.

Kansas City was blown out for a second-straight week, losing 44-3. With Barry and Charles possibly out for the year, there's little hope on the horizon, a sobering turnaround for a team that won the AFC West last season.