ORCHARD PARK, N.Y. (AP) - Rookie quarterback Jeff Tuel and the Buffalo Bills had the Kansas City Chiefs right where they wanted them, only to let it slip away.
The unbeaten Chiefs converted three Bills turnovers into 17 points, including two returns for touchdowns, in a 23-13 victory Sunday.
''I'm definitely frustrated,'' Bills coach Doug Marrone said.
Buffalo (3-6) held a 10-3 halftime lead when it received the ball to start the second half. Buoyed by a 61-yard run by C.J. Spiller, the Bills moved 79 yards to the Kansas City 1. After two failed runs by Fred Jackson, Sean Smith intercepted Tuel and returned it 100 yards to tie the game.
''We earn ourselves a job to get down there and we don't finish it,'' Marrone said. ''We wound up throwing a pick, and not only did we throw a pick, we threw a pick 6.''
Making his first NFL start, Tuel went 18 of 39 for 229 yards with a 59-yard touchdown pass to Marquise Goodwin and two interceptions.
Tuel took the blame on Smith's interception.
''That was 100 percent my fault,'' he said. ''Something I've got to see and I can't do that. We've got to finish with a kick, no matter what, whether an extra point on a touchdown or a field goal.''
Marrone was flabbergasted by the play.
''The guy comes off of Stevie Johnson, just comes off of him, doesn't cover him and was standing right there when we're throwing the ball right into the slot,'' he said. ''Either they knew exactly what we were doing or it's just unbelievable.''
The teams traded field goals before the Chiefs (9-0) turned another Bills turnover into a touchdown. T.J. Graham caught a pass over the middle before being stripped by defensive back Marcus Cooper. Tamba Hali picked up the fumble and returned it 11 yards for a touchdown.
''Turnovers,'' Marrone said. ''It always comes down to that first.''
Tuel, an undrafted rookie, started in place of interim starter Thad Lewis, sidelined with bruised ribs. Buffalo's rookie starter, EJ Manuel, missed his fourth game with a sprained right knee.
Marrone said the Bills still have a chance at the playoffs and he'll use the frustration of this loss to propel them going forward.
''I'm going to use that type of energy,'' he said. ''I'm going to go home. I'm not going to talk to anybody. I'm just going to shut it down. I'm going to be by myself. I'm not going to pet my dog. I'm going to get fired up and I'm going to come to work.''
The Bills outgained Kansas City 470 yards to 211. Buffalo ran 24 more plays and its defense limited the Chiefs to 3 for 13 on third down conversions.
Kansas City remained the NFL's only undefeated team and matched the best start in franchise history set in 2003. The Chiefs now enter their bye week before a key AFC West showdown against Peyton Manning and the Denver Broncos (7-1) on Nov. 17.
''I've heard it said that we haven't played winning teams,'' Chiefs linebacker Derrick Johnson said. ''We're the best you can be at 9-0 right now. If you can't respect that then we're just going to keep winning.''
The Chiefs held an opponent to 17 points or fewer for the ninth straight time - matching the NFL record set by the Atlanta Falcons in 1977. And they extended their impressive worst-to-first turnaround under first-year coach Andy Reid, who has transformed a franchise that finished with a league-worst 2-14 record last season.
Chiefs safety Kendrick Lewis also had an interception, picking off Tuel's pass that sailed over the head of tight end Scott Chandler in the second quarter. That led to Ryan Succop's 27-yard field goal. Succop also hit from 41 and 39 yards.
The Chiefs' offense, meanwhile, wasn't going anywhere. Alex Smith finished 19 of 29 for 124 yards passing. Running back Jamaal Charles had 90 yards rushing but only 6 receiving in being held under 100 yards from scrimmage for the first time this season.
The Bills ran all over the Chiefs' defense in finishing with a season-best 241 yards rushing. Buffalo was led by Spiller, who had 116 yards rushing.
Buffalo travels to Pittsburgh for Week 10.
NOTES: Rookie receiver Robert Woods was taken off the field after injuring his lower left leg while diving for a deep ball from Tuel late in the third quarter. Marrone said the Bills initially suspected a bone injury because Woods could not put weight on the leg, but X-rays were negative. ... Goodwin sustained a hamstring injury and was led off the field with 2:13 to play.