Monte Kiffin is willing to accept responsibility for the Dallas Cowboys' defensive struggles and said it is unfair to blame Tony Romo for Sunday's 51-48 loss to the Denver Broncos.

Romo's fourth-quarter interception led to Denver's winning field goal. But Kiffin's defense surrendered 517 total yards and couldn't stop Peyton Manning who threw for 414 yards and four touchdowns.

"We're working at it" Kiffin said after Wednesday's practice. "We got to play better that's for sure. The other night was not good and we just go back to work and get better.

"I wanna say this: People will say 'Tony Romo throws the interception and we can't win the big one.' He went toe-to-toe with one of the best ever in the game of football and will be in the Hall of Fame. But don't put that on him; you put that one on me. But don't put that one on Tony Romo. We got to play better. We do."

The Cowboys' defense has allowed three quarterbacks -- Eli Manning Philip Rivers and Peyton Manning -- to throw for more than 400 yards this season. In the past two games the Cowboys have given up 1028 total yards.

Kiffin said he couldn't remember a defense he's coached that's allowed so many yards. Overall the Cowboys have the 28th-ranked defense in the NFL. They are fourth against the run but next-to-last against the pass.