ENGLEWOOD, Colo. -- A 3-1 start is not a mandate for how things will go for the Denver Broncos after this week's bye, but it offers a glimpse the Broncos may have found answers to what were their biggest offseason questions.

They are ranked No. 1 in run defense, No. 3 in rushing offense and safety Justin Simmons has already put a win-preserving interception on his résumé as a first-year starter.

"I think that's true," said cornerback Chris Harris Jr. "We had to get some things worked out and I think we did. Everybody knows we started 4-0 last year and didn't make the playoffs, but so far we've done some things better."

Start with the run defense. The Broncos were a dismal 28th in the league last season, having allowed 135.2 yards per game on the ground.

And that meant, despite fielding a unit that led the league in pass defense for the second consecutive year and was ranked No. 4 overall, the Broncos weren't able to close the deal in enough games as opponents simply pounded away on the ground. But the defensive line got plenty of attention in the offseason, including the addition of nose tackle Domata Peko.

Peko's arrival and some defensive tweaks to get the linebackers more involved around the line of scrimmage have contributed to the most drastic improvement the Broncos have made anywhere on the field. The Broncos have allowed just 50.8 yards rushing per game and held Melvin Gordon, Ezekiel Elliott, LeSean McCoy and Marshawn Lynch to a combined 95 yards rushing and no rushing touchdowns in the first four games.

"We want to be the best defense, and in order for us to be the best defense, we have to take out all the top dogs on offense," said linebacker Shaquil Barrett. "We have those guys on our schedule, so we can prove against the top offensive lines that we are great."

The Broncos' own run game, which consistently frustrated former coach Gary Kubiak -- he called it "one of my biggest disappointments last season" -- has flourished. The Broncos' new arrivals on the offensive line -- rookie left tackle Garett Bolles as well as free agents Ron Leary, Menelik Watson and Allen Barbre -- have helped power an offense that has rushed for 143 yards per game.

The Broncos will continue to try to divvy up the carries among running backs C.J. Anderson, Jamaal Charles and Devontae Booker. But coach Vance Joseph made running the ball a priority, and the Broncos have rushed at least 30 times in each of their wins so far this season.

"It's just game by game, day by day, and it starts with practice," Anderson said. "... We definitely emphasize it so much more. ... We can all pretty much be on the same page and that's something that we want to keep doing."

And then there's Simmons, the second-year safety whose emergence in training camp and the preseason was the biggest reason the Broncos released T.J. Ward in September when rosters league-wide went to 53 players. Ward had been to two of his three career Pro Bowls in his time with the Broncos. He was an important voice in the team's locker room, and his departure fueled plenty of drive-time conversation on the local airwaves.

But Simmons has shown to be a sure tackler, and his leaping interception in the closing minutes of Sunday's 16-10 win against the Oakland Raiders was, his teammates said, an example of the athleticism he brings to the position.

"I think Justin has played better the last two weeks," Joseph said. "The first couple of weeks I thought he played a little cautious. [Sunday] and in Buffalo he played like Justin should play. He has great range. He's a great athlete and he's a smart guy. He's playing with more confidence as we play more here."

"There are obviously big expectations," Joseph said. "T.J. was a huge mentor to me and he was like a big brother, and so I wanted to do well, not only for Broncos Country, but for him as well. He helped me so much my first year and still to this day. ... Whether T.J. stayed or left, there would have been big shoes to fill regardless."