Keep scoring, Peyton. But Broncos, you can exhale.

The Broncos suffered another injury to their defense Wednesday when weakside linebacker Danny Trevathan suffered a knee injury.

The Broncos had a scare, but they were relieved to learn an MRI exam on Trevathan’s knee was negative.

The Broncos believe Trevathan will be able to play Sunday against Dallas.

Trevathan underwent an MRI exam Wednesday afternoon. His injury could have been ill-timed, as the Broncos’ best linebacker, Von Miller, remains suspended for two more games and top backup linebacker Paris Lenon is suffering from a strained quad.

With Wesley Woodyard starting at middle linebacker and Nate Irving filling in for Miller on the strongside, the Broncos would have turned to Steve Johnson to replace Trevathan at weakside linebacker.

Johnson had a blocked punt, scoop and score last Sunday against Philadelphia.

“My goal coming into the season was to be a starter,” said Johnson, a second-year undrafted free agent from Kansas.

“That didn’t happen. I don’t wish anybody getting hurt but if I’m asked to step up and get on the field, like I told Wood when we came off the field today: I looked him in the eye and said I will not let you down.’ If I get some playing time, I’ll be ready.”

Even with Miller’s suspension, cornerback Champ Bailey missing the first four games with a foot injury and offensive tackle Ryan Clady suffering a season-ending foot injury in week 2, the Broncos are 4-0 primarily because quarterback Peyton Manning and the offense are outscoring any problems.

The Broncos are averaging 44.75 points through their first four games.

Mike Klis: mklis@denverpost.com or twitter.com/mikeklis