DENVER — From the start, I never completely dismissed the importance of an NFL preseason.

In 2005, my first year covering the Broncos, quarterback Jake Plummer had a terrific preseason, completing 65.7 percent of his passes with three touchdowns against zero interceptions and a 123.6 passer rating.

He then went on to have the best season of his career, throwing just seven interceptions in 16 games and leading the Broncos to a 13-3 record and the AFC Championship Game.

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The next year, in 2006, Plummer felt the pressure of a first-round rookie named Jay Cutler and he wasn’t nearly as efficient in the preseason, completing just 55.9 percent of his passes and posting an 86.2 rating.

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It was a preview of tougher days ahead. For Plummer, his final days. He was pulled in favor of Cutler after game 11 – many believe unfairly – and Plummer wound up retiring after that season at just 32 years old rather than accept a trade to Tampa Bay.

There have been other years when the Broncos’ preseason was a poor indicator. Vance Joseph’s first season as Broncos’ head coach, for instance. The Broncos went 4-0 in the 2017 preseason, and started 2-0 in the regular season, only to finish 5-11.

But first impressions are difficult to shake and I’ve always felt preseasons can matter. These 2019 Broncos, as we will soon know them, have not shown much so far in this preseason. Joe Flacco and the Broncos’ running game had one, nice, 12-play drive against Seattle’s No. 2 defense 10 days ago.

And Von Miller and the Denver defense held the Seahawks’ No. 2 offense to zero points in two series.

But that’s it for the good guys through two preseason games. The preseason game Monday night against the San Francisco 49ers will provide a great sample for Broncos starters. Even No. 1 receiver Emmanuel Sanders is going to play after coming off surgeries to both ankles this offseason.

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Here’s a Klis List of what the Broncos should try to accomplish in their preseason test against the 49ers:

Show something

It’s the first home preseason game of the year and to mark the occasion, Broncos head coach Vic Fangio is expected to play his starters into the second quarter against the 49ers.

A little longer that usual, perhaps, but the first-stringers may also play less than usual in the next-to-last preseason game at Los Angeles on Saturday.

Why? One reason is it was a long time between games leading into the preseason contest against San Francisco while it will be short week heading into the Rams game.

So the game Monday will be the best tune-up for Flacco, Miller and the Broncos’ starters.

RELATED: Sanders credits work ethic, Elway's faith for comeback from two ankle surgeries

Stay healthy

The first two preseason games had two significant injuries in each. Linebacker/special teamer Joe Jones (partially torn triceps), fullback/special teamers Andy Janovich (partially torn pec) and receiving running back Theo Riddick (shoulder fracture) are all expected to miss the early part of the regular season.

Defensive lineman Billy Winn won’t come back at all from his partially torn triceps.

The Broncos could use a little medical luck in preseason game No. 3, especially with the first stringers playing their share.

One catch for Emmanuel 

The Broncos' No. 1 receiver went down with an Achilles injury last December and the Broncos lost their final four games. This will be Emmanuel Sanders' first game back since he had surgery on his left  Achilles in December and right ankle in January. He is instant energy for his team and the crowd. Get him the ball to boost his confidence and get the home crowd going.

Broncos Football Drew Lock
Denver Broncos quarterback Drew Lock (3) takes part in drills during an NFL football training camp session Monday, Aug. 5, 2019, in Englewood, Colo. (AP Photo/David Zalubowski)
(AP Photo/David Zalubowski)

Lock continues to develop 

After Flacco leaves probably at some point in the second quarter, rookie quarterback Drew Lock is expected to again get two quarters of work. He improved significantly from his first professional test against Atlanta in the Hall of Fame Game to game 2 at Seattle.

But during his post-practice presser Saturday, Lock alluded to needing to do a better job of reading the pass rush.

“I think my biggest thing was … just to be more conscious of if they didn't bring two to this side or one this way and one this way because you are in five-man look,’’ Lock said. “Let’s get that mind going so I don't have to take some of the hits that I did in the last game and complete some balls that I need to where we can extend some more drives.”

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Block DeForest Buckner and 49ers front 

The Broncos’ offensive line didn’t match up well against the 6-foot-7, 295-pound interior specimen during the first day of the team’s joint practices Friday. Buckner wasn’t quite as disruptive on Day 2. But now the lights go on.

Stay poised 

Tempers flared in the second of the two-day joint practices between these two teams Saturday. Chances are there is going to be a 49ers player or three who a Broncos' player or four can't stand come game time. Which is fine so long as emotions don't lead to negative consequences. 

Return of Wadmania 

Not returns. But a bounce-back punting performance from Colby Wadman. He was booting a little low and down the middle on two of his punts at Seattle.

Find a returner?

Before it’s too late, someone has to do a good job of fielding and returning punts to keep general manager John Elway from finding one who is not currently on the team. Kelvin McKnight, Devontae Jackson, River Cracraft and Nick Williams are the top candidates.

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49ers BRONCOS tonight