Call the Chiefs lucky or call them opportunistic. Certainly they were both on Sunday and their charmed season continued with a 23-13 victory over the Buffalo Bills at Ralph Wilson Stadium.

The Chiefs didn’t score an offensive touchdown …but their defense produced two touchdowns -- a 100-yard interception return by cornerback Sean Smith that tied the game in the third quarter and an 11-yard fumble recovery by Tamba Hali that gave Kansas City the lead for good.

The victory kept the Chiefs, 9-0, undefeated going into their bye week and leading up to their showdown on Nov. 17 at Denver, 7-1, which was idle this weekend.

The Chiefs’ last three wins have come by one point, six points and seven points.

Buffalo, which started rookie quarterback Jeff Tuel, who began the season on the practice squad, fell to 3-6 in losing to the Chiefs for the first time since 1986.

The Chiefs defense scored for the second time early in the fourth quarter when cornerback Marcus Cooper jarred the ball from Bills receiver T.J. Graham, who had taken three steps after a reception, and outside linebacker Hali scooped it up and returned it 11 yards for a 20-13 lead.

Buffalo’s Dan Carpenter made a 30-yard field goal with 20 seconds left in the third quarter, tying the game at 13.

Just when it appeared Buffalo was going to seize control of the game, Tuel made a fateful mistake on the first possession of the second half.

Buffalo, leading 10-3, reached the Chiefs’ 1 after a 69-yard run by C.J. Spiller and a pass interference penalty in the end zone on linebacker Derrick Johnson.

After two runs by Fred Jackson lost a yard to the 2, Tuel tried threading a pass to tight end Scott Chandler, but threw it right into the hands of Chiefs cornerback Smith, who intercepted the pass at the goal line.

Smith sailed down the sidelines, escorted by Johnson, for a 100-yard return. Instead of trailing 17-3 or even 13-3, the game was tied 10-10 with 10:58 left in the quarter.

Smith’s 100-yard return tied for the second-longest interception in club history. Gary Barbaro, inducted into the club’s Hall of Fame this year, had a 102-yard return on Dec. 11, 1977 against Seattle. Tim Collier had a 100-yard return a week later at Oakland.