Cassel was careful with the football all season, throwing just three interceptions in eight regular-season home games. But against Ray Lewis, Ed Reed and the rest of the Ravens' defense, he completed just 9 of 18 passes for 70 yards.
"You can't turn the football over and expect to win," Chiefs coach Todd Haley said. "You can't take sacks, and you can't give up scoring opportunities in playoff games. Every point's going to count."
Cassel's second interception, late in the third quarter, was converted into a touchdown that extended Baltimore's lead to 23-7.
"I forced a few balls in there, and it did not turn out well," said Cassel, who credits New England's Tom Brady with helping him develop into an NFL starter. "As leader of the team and a leader of the offense, I can't do that.
"Our hats go off to the Ravens. They have a good defense. We knew that coming in. Hopefully, they do well going forward. But this one definitely hurts a little bit."
When Brady was hurt in the 2008 season opener, Cassel came off the Patriots' bench and led them to an 11-win season -- but they missed the playoffs. And the Baltimore defense is a tough foe for any playoff rookie.
"We went into the half down, 10-7, and the game was in reach," said Cassel. "We got into the second half, and it was just a lot of bad football on our part."
Cassel threw his third interception near the end of the game.
"Somehow you just have to stop the bleeding, and we weren't able to do that," he said.
Copyright 2011 by The Associated Press