DENVER—Imagine if the Denver Broncos hadn't wasted seven months during the offseason going through the senseless exercise that was The Great Quarterback Competition.

How good would Trevor Siemian be playing if he had every first-team practice rep, as we can all now agree he clearly should have, from April to August instead of splitting them 50-50?

In the Broncos' thorough, 42-17 whipping of the supposedly strong Dallas Cowboys here Sunday at eventually-to-be-renamed Sports Authority Field at Mile High, Siemian delivered his statement game to NFL nation. By throwing for four touchdowns in what at times appeared to be an easy, pitch-and-catch performance, Siemian showed America and America's team what Broncos fans and the Broncos themselves have gradually come around to realizing.

He’s a pretty good quarterback.

"I think we played well, the Denver Broncos played well,'' Siemian said, deflecting praise for perhaps 200th time in a row since he became the team's quarterback in 2016. "That's one of the things when we came in, we wanted to play complementary football. To beat the good teams in this league, you've got to play well together, everybody across the board, offense, defense, special teams.''

Then again, maybe his offseason-long competition with first-round draft pick Paxton Lynch toughened the seventh rounder Siemian, sharpened his focus. He completed 22 of 32 passes for 231 yards and four touchdowns for a 116.0 passer rating.

Give Broncos head coach Vance Joseph -- who still hasn't experienced the feeling of defeat through four preseason and two regular-season games -- offensive coordinator Mike McCoy and defensive coordinator Joe Woods for their wise game plans against a Cowboys team that finished 13-3 last year and won convincingly against their rival New York Giants in their season opener last week.

On defense, Woods stacked the line of scrimmage with an extra man or three and mixed up his secondary so that Chris Harris Jr. sometime played cornerback and sometimes played safety. It was a plan that focused on loading up to stop Cowboys star running back Ezekiel Elliott -- which can be done when you trust your defensive backs to win one-on-one battles against Dallas receivers.

The idea was if you take away Elliott, quarterback Dak Prescott wouldn't be as effective passing without a real threat of a play-action fake. Elliott came in with 15 consecutive games of at least 80 yards rushing, which tied Marcus Allen for an NFL record. But against the Broncos he had just 8 yards on 9 carries.

"They are built for third down and getting up and rushing the passer, and they did a good job playing to their strength today,'' Elliott said.

Broncos outside linebacker Von Miller snapped his five-game sack drought by dropping Prescott twice in the final 4 1/2 minutes. But Prescott was constantly in harm's way because Elliott couldn't run.

"On film you see guys playing scared against them,'' said Broncos' defensive end Derek Wolfe, who was terrific against the run. "We were like, nah, let's go get him. As soon as the ball was in his hands we were on him. The idea was to make (Dak) Prescott beat us because we knew he couldn't.''

Prescott, the NFL’s Offensive Rookie of the Year last season, was 30 of 50 passing but for only 238 yards with two touchdowns and two interceptions, one to Chris Harris Jr. and another to Aqib Talib, who returned it 103 yards for a touchdown to finish the scoring in the final minute.

On offense, McCoy figured out the Cowboys depleted secondary had no chance against the Broncos' receivers led by Demaryius Thomas and Emmanual Sanders, who were effective on Denver's first offensive series that ended with a touchdown.

"We knew with their starters out they would have trouble covering our receivers,'' Joseph said. "But the run game, that was the jump-starter. We wanted to run the football and force those guys to play single-high (safety) and get 88 (Demaryius Thomas) and 10 (Emmanuel Sanders) one on one. We knew it would be our advantage, our receivers versus their DBs. We knew it would be an edge for us. Obviously running the football helped that edge.''

Thomas had six catches for 71 yards and Sanders had six catches for 62 yards and two touchdowns. C.J. Anderson was a big part of the receiving game and was a huge factor in the running game in what was one of his best all-purpose performances since his breakout year in 2014.

Anderson rushed for 118 yards, including a 23-yard touchdown burst late in the third quarter that gave the Broncos a convincing 35-10 lead, on 26 carries. He also had three catches for 36 yards, with 16 coming on an impressive catch-and-run touchdown in the second quarter.

Anderson's effort was complemented by veteran Jamaal Charles, who still has the speed and quickness to rush for 46 yards on just nine carries.

"I'm just trying to fill my role behind C.J., one of the best running backs in the NFL,'' Charles said.

Is Charles, a five-time 1,000-yard rusher with the Kansas City Chiefs, surprised Anderson is this good?

"No, I've been seeing C.J. play for a while, I knew what he could do,'' Charles said. "He always made plays when he came to K.C. I played with him in the Pro Bowl, so when you get moments like this, it's no fluke.''

After rushing for 140 yards last week in a season-opening win against the Los Angeles Chargers, the Broncos ran for 178 yards against the Cowboys, who ranked No. 1 in defending the run last year and allowed just 35 yards rushing to the New York Giants last week.

"Yeah, but the thing is, I've watched these men in this locker room work every single day,'' said Broncos right guard Ron Leary, who returned from a concussion this week to play against his former Cowboys. "I see it in the weight room. So I know what we were capable of. Nobody gave us a chance and all we do is believe in each other. And when you do that you get the performance that we had.''

Talib iced the game with his 103-yard interception return for a touchdown with 53 seconds remaining. It was the 10th pick six of Talib’s career and sixth in four seasons with the Broncos. Only Rod Woodson (12), Charles Woodson (11) and Darren Sharper (11) have more career touchdowns off interception returns.

"I thought it was going to be an easy one,'' Talib said. "(Cowboys receiver Cole) Beasley came out of nowhere. I seen him at the last minute and I just had to get big on him and get my Bo Jackson on and slide off him.''

He then paused with his story.

"I'm,'' he said, smiling. "And then B-Marsh (Brandon Marshall) escorted me into the end zone. Once he got the quarterback, it was done deal then.''

Talib knows 10 pick sixes puts him past three Hall of Famers who had 9 -- Deion Sanders, Aeneas Williams and Ken Houston -- and is just two away from all-time leader Rod Woodson, another Hall of Famer.

"Ten is a big deal, man,'' Talib said. "I've got to find a way to get three more.''

The Broncos are now 2-0 with their next game next Sunday at Buffalo. The Cowboys, who were favored by 1 to 3 points even though the game was in Denver, fell to 1-1.

Dallas was really never in it as its injury-riddled secondary couldn’t keep up with Denver’s receivers running combination passing routes. Star cornerback Orlando Scandrick was out with an injury and during the game, two more cornerbacks – former University of Colorado standout Chidobe Awuzie (hamstring) and Nolan Carroll (concussion) -- were lost with first-half injuries.

The Broncos lost starting left tackle Garett Bolles to a serious ankle injury and receiver Bennie Fowler III to a concussion. Bolles was carted off the field. At the time, the Broncos' medical team feared he had suffered a fractured tibia near the ankle, but X-rays taken during the game were negative. A more conclusive diagnosis will occur after Bolles has an MRI on Monday morning. There is hope he suffered a severe high ankle sprain, which could still knock him out four to six weeks but would not be a season-ending injury.

"I'm good, boss,'' Bolles said as he hobbled out of the stadium with a heavy boot on his left ankle and cane-like device in his right hand. "We've got Buffalo next week.''

Siemian was 22 of 32 for 231 yards and four touchdowns. He did have two turnovers that led to the Cowboys’ two touchdowns – one off a sack fumble, and the other off an interception when it appeared Thomas ran the wrong route.

"It was just a miscommunication,'' Siemian said "It stinks, but a miscommunication and a bad break.''

Still, Siemian is the 5th-rated NFL passer among quarterbacks who have played two games with a 106.9 rating. .

His touchdown throws were of 10 yards to Emmanuel Sanders on a nice touch pass over three defenders in the back of the end zone; 16 yards to Anderson, who smoked a Dallas linebacker out of the backfield and sped in; 6 yards to Sanders off a misdirection rollout right; and 2 yards to tight end Virgil Green, again off a misdirection roll right.

"Oh man I love Trevor,'' Leary said. "Trev is calm, cool. He doesn't get too high, doesn't get too low. He's steady. I love him.''

Siemian led the Broncos to a quick 7-0 lead off his first series, but momentum was lost in part because of a one hour, 2-minute lightning delay. Joseph immediately ordered the locker room attendants to turn the air conditioning off so the players could stay warm. And he ordered the TV sets on so the players could watch the other NFL games and relax.

The Cowboys got back in the game when edge rusher DeMarcus Lawrence strip sacked Siemian and Dallas got the ball at the Denver 3.

Two plays later, Dallas quarterback Dak Prescott tied it 7-7 with a 3-yard touchdown pass to Dez Bryant.

But after the Cowboys got their gift touchdown early in the second quarter, Siemian calmly led the Broncos on an 81-yard drive that ended with his touchdown pass to Anderson.

It was the type of win that will get the Rocky Mountain Region excited the Broncos can become a playoff team again.

"They're still a good team,'' Wolfe said of the Cowboys. "It's just about winning your one-on-one matchups. Just do your job. And if enough people win, you can kick ass. It's fun. Winning's fun.''

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