ENGLEWOOD, Colo. --How do you fix third downs?

You start by trimming the big mistakes. On three third downs against the Kansas City Chiefs on Sunday, the Broncos committed penalties that resuscitated possessions. With those included, that took the Chiefs up to 14-of-19 at extending drives once they got to third down.

These are the most obvious correctable mistakes that emerged from the film study of the 24-17 Week 2 win.

"We had a lot of dumb penalties, we had some offsides, we had some roughing the passers, and some mental breakdowns when we just couldn't get off the field," said cornerback Chris Harris Jr. "A lot of those times, the reason why weren't getting off the field on third down was ourselves, what we're doing."

Added linebacker Brandon Marshall: "We've just got to keep our composure. We did a lot of things to hurt ourselves.

"I mean, we're a resilient group, definitely, and I think you saw that the first week, and now you saw it this week, so even though some bad things happened to us, we eventually come out and we make a big play."

Next, you apply the lessons from the third-down stops the Broncos made the last two weeks. In particular, the Broncos can learn from the series where third-down stops were followed by big fourth-down stands that finished the job, including two against Indianapolis and the final goal-line stand Sunday.

In both games, the Broncos had to account for mobile quarterbacks whose arms can make surgical strikes. That will be the case again Sunday in Seattle, as the Broncos learned first-hand when they faced Russell Wilson in Super Bowl XLVIII and in preseason games in August 2012 and 2013.

"We'll watch the film and see what they did, or what we could do different, and nip it in the bud before we go to Seattle next week and see a quarterback who does the same thing and has explosive players at receiver," said defensive tackle Terrance Knighton. "We'll just keep improving, and it's good that we're getting this test early and building character for our defense and responding."

And the final step is simple: for defenders to become accustomed with one another. This is a defense still in the gestational phase of becoming a cohesive unit.

"It's going to take a little bit more time than everybody expected," said Harris. "That's part of the game, man."

Eight of the 11 starters Sunday were not in the defense's starting 11 in Super Bowl XLVIII; eight of the 10 defenders who played more than 50 snaps against the Chiefs were not on the 53-man roster by the end of the 2013 season.

"Everybody's so new, and we have a lot of guys still coming back. It's going to take a minute for us to gel," said Harris.

But before Harris finished that thought, he returned to the self-inflicted wounds.

"We've just got to continue to practice and not beat ourselves," he said. "Once we stop beating ourselves, having dumb penalties, dumb missed assignments, then we should be good."

But in the meantime, two questions loom: how much improvement can the defense make on third downs before facing the defending world champions, and will it be enough?