DENVER—Trevor Siemian may have been an afterthought. He may have been unheralded, inexperienced and a seventh-round longshot.

He is also going to be the opening day starter for the defending Super Bowl champions.

After struggling to find a rhythm amid a flurry of early running calls, Siemian finished the first half with two scoring drives. Rookie quarterback Paxton Lynch led a touchdown drive on the second series of the second half to help push the Denver Broncos past the Los Angeles Rams, 17-9 on a pleasant, late-August evening Saturday at soon-to-be-renamed Sports Authority Field at Mile High.

"I'm impressed,'' Broncos head coach Gary Kubiak said of Siemian following the game. "I think he's very calm. I can tell by the way he handles the team in the huddle. He has control of what's going on. He gets a bad break on the "go" ball but he comes right back and goes right down the field. What I see is a guy getting better.''

Based on how Kubiak has handled his quarterback situation the past two seasons, he will likely tell his players at their team meeting Monday morning that Siemian will be their starting quarterback when the regular season begins Sept. 8 with the NFL's kickoff game against Carolina.

"I'm confident,'' Siemian said. "Ultimately that is up to Kubes. That is a better question for him. We will see what happens and be the best team we can be.''

The Broncos, 2-1 in the preseason, have one last preseason game Thursday at Arizona, where only the reserves figure to play.

Siemian finished the half completing 10 of 17 passes for 122 yards, including a 1-yard touchdown toss to Virgil Green. Siemian was also intercepted once when it wasn’t really his fault but had another interception dropped.

He’s still learning, too.

Lynch, a first-round rookie, was the Broncos’ second quarterback to play in the second half. He mixed in two completions between strong runs by tailbacks Devontae Booker and Ronnie Hillman during a touchdown drive that Hillman capped with a nice, 7-yard touchdown run in the third quarter.

Lynch started the second half working with the second-team offense. He began 4 of 4 for 32 yards, but he missed on his next five pass attempts and finished 6 of 13 for 57 yards.

His best pass came on third-and-7 from his own 15 and the Broncos trying to run out the final 3 minutes, 13 seconds. Lynch came through with a 16-yard dart to former Memphis teammate Mose Frazier on a skinny post.

"First, I think that I just feel more comfortable," Lynch said. "I've had a chance to see a couple of defenses now so I'm not so surprised by what's going on, but we moved the ball a little bit. I wish we could have scored more touchdowns, but overall, we won the game and we played good as a team.''

Mark Sanchez, the eight-year veteran who for most of the offseason was considered the man to beat in the Broncos’ quarterback competition, did not play Saturday night. Sanchez actually has the best quarterback rating of the three with 85.3 to Lynch's 78.3 and Siemian's 70.4. But now that Sanchez is essentially the No. 3 quarterback, it would be surprising if the Broncos didn’t release him in lieu of his $4.5 million salary and a seventh-round draft pick Denver would have to give the Philadelphia Eagles if he makes the 53-man roster.

Siemian seemingly did enough in the first half to clinch the Broncos’ starting quarterback job that for most of the offseason was Sanchez’ to lose. He lost it by committing three turnovers in the Broncos’ first two preseason games.

Sanchez’ $4.5 million salary has $1 million guaranteed and the team would be charged with a $1 million “dead money” hit against its salary cap, but it would also save a seventh-round draft pick.(Editor's Note: It was previously reported here none of Sanchez's $4.5 million salary was guaranteed. He does have $1 million guaranteed). Still, the Broncos are likely to consider the remaining $3.5 million too rich for a No. 3 quarterback, especially when they want Lynch to continue to get practice reps).

The Broncos had acquired Sanchez from the Philadelphia Eagles in March in exchange for a conditional draft pick. The conditions: If Sanchez started a certain number of games, the Broncos would give Philadelphia a sixth-round draft pick. If he made the 53-man roster, the Eagles would get the Broncos’ seventh-round pick. If he didn’t make the Broncos’ roster, the Eagles would not get a draft pick.

A month after acquiring Sanchez, the Broncos got a sixth-round draft pick from the New York Jets in exchange for left tackle Ryan Clady. That sixth round pick was not by accident – the Broncos figured it would offset their own sixth-round pick they would likely have to give Philly for Sanchez.

It didn’t work out that way. Siemian completed 4 of 5 passes during a 67-yard, second quarter drive that culminated with his toss to Green.

That gave the Broncos a 7-6 lead with 4 minutes remaining in the half. The Rams behind rookie quarterback Jared Goff drove down for Greg Zuerlein’s third field goal to recapture the lead, 9-7.

But with 40 seconds remaining, Siemian connected with Demaryius Thomas on a gorgeous, 43-yard pass-and-one-handed snag that set up Brandon McManus’ 50-yard field goal with 12 seconds remaining.

For a while it appeared Siemian was going to stamp his quarterback competition victory without trying. The Broncos first series was three plays, three runs, punt. Their second series was three plays, three runs, punt.

Siemian came out throwing on the third series, but after connecting with Emmanuel Sanders for an 11-yard, move-the-chain completion on third-and-10, and the possession died when C.J. Anderson was swarmed and stuffed on a fourth-and-1 at the Denver 45.

Siemian started getting warmed up when the Broncos got the ball back at their 25 with 11:31 left in the half, down 6-0. On consecutive passes, Siemian hit first Thomas and then Sanders for first downs.

Then came a tough bounce. Siemian tossed deep to Cody Latimer, but the pass was slightly underthrown. As Latimer battled Trumaine Johnson for the ball, it was deflected into the arms of safety Cody Davis near the goal line.

But Siemian bounced back and now the seventh-round draft pick – who threw 7 touchdown passes against 11 interceptions in his senior year at Northwestern – is in line to replace the retired Peyton Manning as starting quarterback for the Super Bowl champs.

The Broncos open their season in 12 days against the Carolina Panthers in a Super Bowl 50 rematch in Denver.

"I've had a blast to tell you the truth,'' Siemian said when asked about what has been four months worth of quarterback competition. "It is a credit to coach (Greg) Knapp, Mark and Pax to push each other. It has been super competitive. Everybody has been good to each other and those are great guys.''