ENGLEWOOD, Colo. (AP) — For the first time since 2014, the Denver Broncos spent their summer without a job-share arrangement at quarterback, something they expect to give them a big boost Sunday when they open against the Seattle Seahawks with Case Keenum under center .

"That's the best thing if you've got one quarterback you can go with," receiver Demaryius Thomas said. "Like, for example, Antonio Brown's been with Ben Roethlisberger since forever. That's why they're so good."

Gary Kubiak spelled Peyton Manning with Brock Osweiler in 2015, and that plan paid off during a special season in which Osweiler stepped up while Manning was sidelined with a bum foot and kept the Broncos' Super Bowl hopes alive until Manning's return.

Protracted quarterback competitions at training camp in 2016 and '17, however, seemed to hinder the team's rhythm and chemistry, two qualities that are so vital in a league where timing is everything.

In 2016, Trevor Siemian beat out veteran Mark Sanchez and rookie Paxton Lynch, and last year Siemian beat out Lynch again but not before the two shared a significant number of snaps with undrafted Kyle Sloter, who wasn't even in the mix for the Broncos' starting job.

Upon signing Keenum to a prove-it two-year free agent deal worth $36 million in March, general manager John Elway declared Keenum as the Broncos' undisputed starter .

The only question, he said, was who would back him up.

While all the drama in QB-crazed Denver this summer centered around Chad Kelly leapfrogging Lynch, the first-rounder who was ultimately cut , for the backup job, Keenum was getting almost all the work with the No. 1 offense.

Thomas and an energized Emmanuel Sanders appreciated the consistency and both had terrific training camps. Thomas said that chemistry puts the offense way ahead of where it was at this time in the last few seasons.

"We've gotten enough run routes, passing plays in," he said with a smile. "So, it was a good thing."

Having an established starter also paid dividends for the O-line.

"Absolutely, you want one guy back there knowing that's your guy and where he sets up and how he controls the offense," left tackle Garett Bolles said.

This in many ways marks Keenum's first time being "The Guy."

Keenum led the Minnesota Vikings to the NFC championship game last season after injuries to Sam Bradford and Teddy Bridgewater.

He started the Rams' opener back in 2016 but he would give way later that year to top draft pick Jared Goff before going to Minnesota and having a career year in which he threw for 3,457 yards with 22 touchdowns and seven interceptions.

The Broncos are his fourth team in six NFL seasons after Kubiak gave him his first chance with the Texans as an undrafted free agent out of the University of Houston in 2013.

His Denver debut got a little more daunting Wednesday when Seahawks safety Earl Thomas ended his lengthy holdout in time for the team's trip to Denver even without a new contract.

Although Seattle coach Pete Carroll wouldn't commit to whether Thomas will play in the opener at Denver this weekend, the Broncos have no choice but to prepare for his presence.

"Earl is a special player," Keenum said. "He's one of the best I've ever played against. I've played him a bunch, watched him a bunch and he does some things on film that nobody else can do."

Missing all of the Seahawks' offseason program, training camp and the preseason makes Thomas no less formidable, either, Keenum suggested.

"He's a guy who you just need to know where he is at all times because he can play his assignment from almost anywhere on the field," Keenum said. "So ... I guarantee you he can step in and be right wherever he wants to be."

Thomas is a three-time first-team All-Pro and was the anchor for the Seattle defense that appeared in consecutive Super Bowls, winning the first in a wipeout of the Broncos.

Seattle used Tedric Thompson as its primary free safety during Thomas' holdout.

Regardless of whether it's Thompson or Thomas that they'll be facing Sunday, the Broncos have a healthy respect for Seattle's stingy defense even though it has lost fellow "Legion of Boom" members Kam Chancellor and Richard Sherman.

The Broncos feel better about their offense, too, after Elway infused his roster with talented rookie receivers Courtland Sutton and DaeSean Hamilton, rookie running back Royce Freeman and second-year tight end Jake Butt, who missed last season on IR.

"I've got a lot of respect for 29," Keenum said of Thomas. "But we trust our guys running routes and catching the ball versus anybody out there."

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AP Sports Writer Tim Booth contributed.

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