ORCHARD PARK, N.Y. — Chiefs cornerback Sean Smith was exhausted after he returned an interception 100 yards for a touchdown.
"I was definitely happy I made it," Smith said. "I wanted to celebrate, but I was too tired."
That's fine, because the Chiefs are breathing easier after their defense kept a perfect start intact.
Smith's interception and linebacker Tamba Hali's 11-yard fumble return for a touchdown helped Kansas City overcome a pedestrian offense Sunday in a 23-13 win over the Bills.
Kansas City remained the league's only undefeated team and at 9-0 matched its best start, set in 2003. The Chiefs have a bye before a key AFC West showdown Nov. 17 at Denver.
If the only thing perfect is their record, first-year coach Andy Reid refuses to apologize.
"We're pretty happy that we got the touchdowns," said Reid, whose team continued its remarkable turnaround from a 2-14 finish last season. "We'll take them any way we can get them."
The Chiefs' defense outscored its Alex Smith-led offense, which produced three field goals. And the defense compensated for its own problems with help from a Buffalo offense headed by quarterback Jeff Tuel, an undrafted rookie in his first career start.
Despite allowing a season-high 470 yards and 25 first downs, the Chiefs held their ninth consecutive foe to 17 points or fewer, matching a record set by the 1977 Falcons.
Smith's interception tied the score at 10 after Tuel had marched the Bills 79 yards in the third quarter. Hali put the Chiefs up for good by scooping up T.J. Graham's fumble, forced by cornerback Marcus Cooper, and running it in to put Kansas City ahead 20-13 with 12:47 left.
The Bills were left stunned and frustrated in attempting to figure out how they let this one slip away.
"Horrible," offensive coordinator Nathaniel Hackett said. "It was shocking even to our guys. We did everything we wanted. We just couldn't finish it."