The Denver Broncos, one of the NFL’s worst teams against the rush in 2016, face three staunch tests in the first four weeks of the 2017 season. The first of those comes this week when the best rushing attack in the NFC last year comes to Denver.

The Broncos (ranked No. 28 against the run last year) looked solid against the Los Angeles Chargers (the No. 26 rushing attack in 2016), allowing only 64 rushing yards in a 24-21 Week 1 victory.

Things get markedly more difficult as the Dallas Cowboys come to town in Week 2.

Last year Dallas averaged nearly 150 yards per game (149.8) to lead the NFC. Denver, which allowed 130.3, went to work this offseason to bolster their run defense. The additions of NT Domata Peko, DL Shelby Harris and DE Zach Kerr have so far been a mixed bag.

Peko was stout against Los Angeles, but played only 46 percent of snaps. Shelby Harris, who made the biggest play of the game, has been a major surprise. A knee injury kept Kerr off the field. The former Indianapolis Colt returned to practice on Wednesday ahead of the matchup with Dallas; his coaches are hopeful he’ll be back on the field Sunday.

“It’s good for our football team,” Head Coach Vance Joseph said Wednesday of Kerr and fellow DE Jared Crick (back) returning to practice.

“With Kerr, facing the Cowboys this week, with a big offensive line that runs the football, that’s huge for us.”

Joseph wouldn’t commit when pressed as to whether or not Kerr would be on the field, but he did sound optimistic.

“Right now, he’s doing fine. As we go along, we’ll see. Right now, he’s definitely getting better fast,” Joseph said.

While health is paramount to Denver’s success (DE Derek Wolfe is also dealing with a lingering ankle injury), the sheer quality of Dallas’ offensive line and backfield are the biggest challenge.

The Dallas O-line is widely regarded as the best in the league, even with the retirement of RT Doug Free.

“It’s an offensive line that three out of five guys were voted to the All-Pro team,” Joseph reminded reporters. “That’s the ultimate team that you can make in this league – not a Pro Bowl guy that was an alternate. They were three out of five first-[team] All-Pro guys. It’s probably the best offensive line in football. It’s going to be a challenge for us. They’re big. They’re athletic, and very, very smart.”

Von Miller, Denver’s three-time All-Pro edge rusher, is very aware of the challenge Dallas presents – even the relative newcomer to the line replacing Free.

“I think it starts with the All-Pros that they have. They have three First Team All-Pros. Left tackle Tyron Smith has been great since day 1, [G] Zack Martin, and [C] Travis Frederick, all of those guys. And then you have [RT] La’el Collins too, he’s great. He was really a steal in the draft, he should have been a first-round pick. If you look at that offensive line, it’s an all-star offensive line.”

Miller will work mostly against Collins on Sunday, with the goal of stopping a dual threat out of the Dallas backfield: Last year’s leading rusher and NFLPA Offensive Rookie of the Year, Ezekiel Elliott, and AP Offensive Rookie of the Year, Dak Prescott.

“Get him on the ground,” Miller says about how to stop Elliott.

Easier said than done. Last year the Ohio State product averaged 5.1 yards per carry, and according to Pro Football Focus averaged 2.6 yards after contact and broke 36 tackles. As PFF pointed out, “Elliott came within 62 yards of topping 1,000 rushing yards after contact [last] season.”

Miller went on to compare Elliott to one of the game’s all-time greats.

“The great running backs like that they can take a little bit of daylight and go all the way with it,” Miller said. “We played [New Orleans RB Adrian Peterson] I think it was two years ago, and he was the same way. At any given time, you can be pitching a no hitter and then boom, homerun towards the end of the game. That’s what happened to us when we played A.P. Even though they’re two totally different backs, they’re both elite. If you give them any type of daylight, which is hard to keep it dark on the offensive line because they have a great offensive line. Any bit of daylight, he can take it the distance.”

Elliott took 15 rushes into the end zone in 2016, six of more than 10 yards and two of more than 55. His average scoring carries went for 14.07 yards. His lone receiving touchdown went for 83 yards.

Joseph shared Miller’s praise for the second-year back.

“You saw it in college with this guy. He has a special talent. He rushed for 1,600 yards last year as a rookie and made it look easy. And he’s a durable guy. He doesn’t take a lot of hits. He runs behind his pads. He’s a great knee-bender. He’s special,” the head coach said.

Even if Denver is able to contain Elliott, they still have to worry about Prescott, who can hurt them with both his arm and his legs.

As a rookie, the Mississippi State product threw for an eye-popping 23-to-4 touchdown to interception ratio and 67.8 completion percentage. He also ran for 282 yards and six touchdowns. His three rushes in Week 1 this year averaged 8.0 yards apiece.

The only knock on Prescott in 2016 was his propensity to fumble when spending too much time in the pocket. Keeping him there will be key for Miller and the Denver D-line.

“Yes, if you have a quarterback that’s rolling out, you’ll definitely be on your toes because he’s athletic, he can roll out and he can throw it and pass it,” Miller said Wednesday. “Whenever you’re against an athletic quarterback like that, you have to be on your toes because it can—he’s a dual threat out there, especially on the outside. I’ve just seen him roll out, the defensive end I have the angle on him and he outruns them and hooks the ball for 15-20 years.”

The Broncos defense has made its living these past few years off a stout pass rush and the best secondary in football. Joseph knows that Prescott and Dallas present a unique challenge for his team as they continue to improve their run defense.

“He is so efficient and the offense is built that way,” Joseph said of Prescott. “They’re a run first, play-action pass team, so when they throw it, after 10 straight runs – that’s preached there.”

The challenges won’t end with Dallas.

The Broncos travel to Buffalo next, to face the top rushing team in football from 2016. The Bills haven’t let up through the first week of the 2017 season; their 190 yards in Week 1 was the best in the league.

After that, it’s the No. 6 rushing offense from last year, Oakland. The Raiders reloaded their backfield by luring Marshawn Lynch out of retirement and he ran for 76 yards in the opener.

The return of Crick and Kerr would be a big lift for Denver against the Cowboys, their first of three major tests to the improved run defense over the next three weeks.