ORCHARD PARK, N.Y. -- Quarterback? Receiver? Play-caller?

Blame who you want, but Jeff Tuel's goal-line interception, returned 100 yards for a touchdown, was the turning point in the Buffalo Bills' 23-13 loss to the Kansas City Chiefs on Sunday.

It couldn't have come at a worse time -- the Bills had a 10-3 lead, received the opening kickoff of the second half, and drove quickly downfield -- and the result couldn't have been more catastrophic.

So what happened? Who deserves fault on the play?

Let's take it blow-by-blow, first setting up the situation: a third-and-goal on the 1-yard line, following two straight Fred Jackson runs for no gain.

"When it got down tight [in the red zone], they did a great job. They would show all-out [pressure], then back up," offensive coordinator Nate Hackett said.

After going big on the first two plays -- both runs -- the Bills spread the field for the third play. Tuel was in a shotgun formation, with Steve Johnson and T.J. Graham aligned to the offensive right.

"Obviously, if you want to run the ball, it sucks. If you want to throw the ball, you have to get it out quick [since] somebody is going to take a shot at you. We wanted to try to combine two things in one," Hackett said.

The play-call, then, was a designed run that could be changed into a pass if the defense showed "all-out" pressure.

"It was a play that was working for us well during the game," coach Doug Marrone said. "If there's an all-out pressure, we pull [the run] and have the ability to throw it. They were in an all-out [look], cover-zero."

"I think it was one of those things, when we threw it to T.J., I took it off of [Tuel]," Hackett said. "I just said 'hang back there and throw a good ball. Because you're going to have so many people coming at you.' I didn't want to have him think too much. So I didn't have him think. I just wanted him to drop back and throw a good ball in that situation."

Tuel correctly read the "all-out" pressure and made the decision to throw to Graham, who cut towards the center of the field at the snap. The problem is that Chiefs cornerback Sean Smith allowed Johnson to run free over the middle, instead stepping in front of Graham's route.

"[Tuel] went to throw the ball to his first read and [Smith] just stopped. Just stood there," Hackett said. "Jeff let it go, from what I could tell. He had a couple of other guys, but he was so into, 'got to get it out, got to get it out,' he just threw it. I think he might have thrown it a little bit blind in that situation."

"[Smith] comes off Stevie Johnson. Doesn't cover him. And he was standing right there when he was throwing the ball into the slot," Marrone said. "Either they knew exactly what we were doing, or it was just unbelievable. I haven't seen a lot of that."

"It was zero coverage all out. 100 percent my fault, something I've got to see," Tuel said. "I can't do that."

So why didn't Tuel see Johnson?

"There were a lot of bodies down there. That's one I have to see on tape and if he could have done something else on it -- I think we had Stevie and some other guys -- but with all those guys up there, we had to have a plan for that," Hackett said.

Would they re-think the play-call?

"Situationally, do you question the play call? No. Do you question the execution of it? Yes," Marrone said. "Should we go in there and try to keep running and work on it? It's a play in the [middle of the] field that we do pull it and throw it, a lot of times down the goal line we don't pull it and throw it. We've got to do a better job coaching it."

"There's two thoughts of it: get big or get small. We did both and both didn't work," Hackett said. "So we just have to get back to the drawing board, go to work, and figure out what we can get done."