ENGLEWOOD, Colo. -- With a pile of touchdowns in their wake to go with more than their share of playoff disappointment over the past three years, John Elway conceded this week there might be some growing pains in the Denver Broncos' offense early in the season as the team transitions to a scheme it hopes can push it closer to a trophy.

The Broncos have scored three touchdowns on offense in two preseason games. Against the Houston Texans last week, the Broncos did not score on any of the four drives led by quarterback Peyton Manning. Manning did not play in the preseason opener in Seattle.

The Broncos do not have a rushing touchdown in their two preseason games, and the starters have finished one drive -- against the Seahawks -- with a touchdown, a Brock Osweiler-to-Virgil Green pass.

“It’s going to be a work in progress through the year, too,’’ Elway said. “We’re not going to be clicking on all cylinders. We’d like to, but ... we know it’s a work in progress for this offense and people are going to continue to get more and more comfortable with it, even after we start the regular season. I think the progress of where we are right now is good.’’

The Broncos were tied for ninth in the league in pass attempts in 2014 and were second in the league in pass attempts in 2013. The Broncos were largely in three-wide receiver sets with Manning in the shotgun as the Broncos averaged 34 points a game over the past two seasons, including Manning's NFL record of 55 touchdown passes in '13.

In the transition to the new coaching staff, Gary Kubiak has installed a more run-heavy attack that likely will have Manning open plays under center far more than he has in recent years. The Broncos will have Manning line up in the shotgun and have worked out of the pistol at times in practice, but in the end, Kubiak has said he believes the Broncos need to be more physical and run the ball far more efficiently to go deeper into the postseason.

Couple that change in schemes with some built-in rest days for Manning, and Saturday’s preseason game against the San Francisco 49ers will be a key yardstick to gauge progress.

Asked if Manning would take a little longer to find a rhythm because the Broncos have built-in off days throughout the offseason to keep him fresher down the stretch, Elway said, “Maybe it’s not what he’s used to, but I just think at 39 years old, he can’t work like he used to work. He’s got to be able to say that. Even though he may not be as far along as he wants to be right now because he hasn’t had that work, he’ll be much farther along in December by taking this time off when he’s really going to need it.’’

Because it is the Broncos’ third preseason game, Manning and the remainder of the starters are expected to play at least a half. Manning played 21 snaps against the Texans, finishing 8-of-14 passing for 52 yards.

“Obviously, we only played 20-something snaps the other night, four series,’’ Manning said. “If we do get to play a little bit more, obviously, it’d be nice to work on that chemistry as a unit and be able to move the ball, convert some third downs and obviously try to find a way to get into the end zone. I think that those are the main things that we’re trying to accomplish, and no matter how long you play, you want to be able to do that. Obviously, if you get to play a little bit longer, it can allow you, hopefully, to get into a little bit of a rhythm where you can maybe do some things.’’

Kubiak said he hoped to have Manning throw to wide receiver Emmanuel Sanders at least some on Friday. Sanders has been held out of practice in recent weeks because of a hamstring injury.

With Demaryius Thomas having skipped the offseason program as the Broncos tried to work out a long-term deal with the three-time Pro Bowl selection, and with Sanders’ injury to go with the Broncos’ rotations in the offensive line, including this week’s signing of guard Evan Mathis, the Broncos haven’t worked with the personnel expected to start the Sept. 13 season opener against the Baltimore Ravens.

Mathis, who just arrived Wednesday, is set to begin practicing next week.

“We’ve got to come out -- we have Baltimore at home -- we’d like to come out fast,'' Elway said. "The goal is always to come out and play well and continue to build off that as the year goes through. I think with a new coaching staff, there are going to be some growing pains early in the year. You just hope that it doesn’t affect you enough where it costs you any football games.”