The defeat snapped the reigning Super Bowl champion Packers' overall win streak at 19 games as Green Bay dropped to 13-1 on the 2011 season.

"I've viewed the undefeated season as gravy. The goal is to get the home field advantage and win the Super Bowl," Packers head coach Mike McCarthy said.

"We were fortunate enough to be in the position to possibly achieve the undefeated season. But we still have the primary goal in front of us, and that's to get home field advantage."

Orton completed 23 of 31 passes for 299 yards in his first start for Kansas City, who sacked head coach Todd Haley after the team dropped five of its last six games.

Quarterback Aaron Rodgers went 17 of 35 for 235 offensive yards for the Packers who lost for the first time since December 19, 2010 when they were beaten by the New England Patriots.

"I think our goal ultimate goal is to win a Super Bowl. The next step is getting that number one seed in the playoffs," Rodgers said. "We've got a home playoff game -- we've got a bye secured."

Rodgers also ran eight yards for a touchdown with just over two minutes left in the fourth quarter.