ENGLEWOOD, Colo. -- It was a practice, so it was a learning experience for the Broncos offense -- even though it was clearly not the type of day they hoped to have.

Running back Phillip Lindsay had a pair of drops, including one that saw the Joe Flacco pass bounce out of his grasp and into the hands of 49ers linebacker Malcolm Smith. He also lost a fumble that was forced by San Francisco linebacker Fred Warner. Warner was also a part of another 49ers takeaway when he burst unblocked through the A-gap, forcing a hurried Flacco throw that San Francisco's Tarvarius Moore intercepted.

Running lanes were scarce and often quickly filled by linebackers. When running back Royce Freeman did find a crease for a 10-yard run to the right flank, it was narrow and through heavy traffic.

Passing windows were small as the Broncos' receivers struggled to separate from tight coverage. On one second-team repetition, quarterback Drew Lock perfectly executed a play-action bootleg, rolling to the right. In previous practices, he was usually able to find an open target in front of him. In this instance, every potential receiver was blanketed by a defender in man-to-man coverage, leading him to tuck the ball under his arm and run.

All that was part of a practice that Offensive Coordinator Rich Scangarello described as "very choppy."

Having worked on the 49ers' coaching staff in 2017 and 2018, Scangarello knew the 49ers' defense would be a challenge for his unit, tossing some different looks and concepts at his players. The 49ers run a base 4-3 formation with a "wide-nine" alignment, in which one of the defensive ends aligns himself in a nine-technique position -- beyond the outside shoulder of the tight end. He keeps his hand in the dirt, but is in a position more typical of a 3-4 strong-side pass rusher.

San Francisco's three linebackers in the formation are also interchangeable, and the 49ers used this to their advantage, with Warner and Smith in particular making multiple plays Friday. With defensive end DeForest Buckner getting to Flacco for multiple rushes that would have been sacks in game conditions, the 49ers defense gave the Broncos a trial by fire.

"He's probably one of the three or four best interior players in this league so yeah, he's always going to be tough to block," Scangarello said, "and if you're not planning around him, he's going to cause problems."

This was a necessary day for Denver's offense, and Scangarello believes that when it returns Saturday, his players can adjust to the speed and looks the 49ers gave them. That would give him an indication that his offense possesses the adaptability it must have.

"It's entirely different than they see every day in practice," Scangarello said. "And that's how it is week-to-week in the NFL, and when you're playing with three groups of offensive lines, a couple of those guys haven't gotten as many reps lately as well, too.