Kansas City, Mo. ? The Kansas City Chiefs rushing defense hasn’t been spectacular in 2007. Before Sunday, it was ranked 17th out of 32 NFL teams. But there’s one thing, linebacker Derrick Johnson says, even a mediocre defense should be able to do with the game on the line.

“You’ve got to stop Oakland,” he said after Kansas City’s 20-17 loss to the Raiders on Sunday. “Maybe we’re not as good as we think we are.”

Oakland’s Justin Fargas ran for 43 demoralizing yards on a game-clinching drive, including a 21-yard scamper off right tackle on third-and-11, and finished with 139.

“We’ll have to watch film, because right now we’re confused about what went on today,” Johnson said. “If you had asked us a week ago, ‘If you have four minutes left, two-minute warning, a timeout, can you stop Oakland?’ Yeah, we’ll put that pressure on anyone who comes in here.”

Kansas City coach Herm Edwards gave Fargas and the Raiders the opportunity to clinch the game when he decided to run the ball on fourth-and-one with 4:26 left, rather than try a game-tying field goal. A pair of linebackers stuffed rookie running back Kolby Smith on the play, and Fargas closed the game for Oakland.

Chiefs kicker Dave Rayner had missed his previous attempt, and three of five dating back to last week, but Edwards said that wasn’t his main reason for sending the offense back out on fourth down.

“We couldn’t stop them from running. I felt that on the sideline, and that’s why I decided that, in field-goal range, we needed to get seven,” Edwards said. “Three points wasn’t going to help us.”

Edwards lost faith in the defense after it surrendered second-half rushing touchdowns to Fargas and Lamont Jordan, squandering a 10-6 halftime lead and a 150-yard, two-touchdown performance from Smith.

“It’s something that we’ve got to stop,” Chiefs safety Jarrad Page said. “It’s been happening where we play a good first half, then we come out and can’t finish the game in the second half.”

Johnson led the Chiefs with six tackles and was at a loss to explain why Fargas averaged 6.3 yards per carry Sunday, a week after K.C. held Indianapolis’ Joseph Addai to a 3.4-yard average.

“Nothing surprised us. They ran no new plays,” Johnson said, shaking his head. “They ran exactly what we practiced.”

The Chiefs fell to 4-7 and will host San Diego next week, with a trip to another division rival, Denver, looming Dec. 9.

“We’re in a bad situation right now,” Johnson said. “It’s going to test our character.”