Chiefs LB Derrick Johnson suffers complete tear of Achilles tendon

— -- KANSAS CITY, Mo. -- Kansas City Chiefs linebacker Derrick Johnson?sustained a ruptured Achilles tendon in his left ankle in the second quarter of Thursday night's 21-13 win over the Oakland Raiders, coach Andy Reid confirmed.

The four-time Pro Bowler, who missed most of the 2014 season because of a torn Achilles, threw his helmet in frustration after the injury. He had to be helped off the field.

"I felt a little bit of a letdown when it Reid acknowledged, "but the last thing D.J. would have wanted was a letdown."

Johnson, who along with punter Dustin Colquitt is the longest-tenured Chiefs player, arrived in Kansas City as its first-round draft pick in 2005. He remains one of the Chiefs' top defensive players, as he rarely comes off the field in running or passing situations.

His backup is D.J. Alexander, a fifth-round draft pick last year.

It was still 21-3 when Johnson went down, and his injury seemed to briefly deflate the Kansas City defense. Oakland proceeded to march 92 yards for its lone touchdown just before halftime.

But the Raiders kept coming up empty with their chances in the second half.

Information from The Associated Press was used in this report.