Inconsistent. Porous. Disappointing. These are just some of the verbal Molotov cocktails lobbed in the direction of the Broncos’ offensive line this season.

A year ago at this time, general manager John Elway began a search for a head coach, desiring a team that would go out “kicking and screaming.” Offensively that meant more running, especially when Gary Kubiak took over as boss after the Broncos’ disappointing one-and-done playoff exit.

During his previous two decades as a coordinator, Kubiak’s rushing attack averaged a 10th-place ranking in the NFL. Through nine games this season, Denver sat in 29th place, averaging only 86 yards per game.

As a makeshift group featuring a blend of extreme youth and experience, the offensive line received the bulk of the external criticism. Then something weird happened. Over the last six games, all of which featured the quarterback under center, the rushing attack breathed to life. Denver averaged 135.1 yards rushing per game, seventh-best during this stretch. In the Broncos’ biggest wins, running back C.J. Anderson walked off the New England Patriots in a snowstorm and Ronnie Hillman left footprints on the San Diego Chargers with a fourth-quarter score.

“We just got better later in the season. We built on some early success,” said center Matt Paradis, who is Denver’s only offensive player to log every snap this season. “In the end, it was just better execution.”

It can be forgotten that transitions are difficult, even at the professional level. Kubiak and offensive coordinator Rick Dennison introduced a zone-blocking scheme, which requires the mastering of cut blocking and mobility through repeated drills. But this is a different NFL than when the Broncos won Super Bowls with this scheme in the 1997 and 1998 seasons. Players rarely practice in pads, and they don’t cut block or take defenders to the ground during workouts anymore.

It means game time, in some ways, becomes practice, making it difficult to microwave the learning curve.

“I think the line has grown up,” Anderson said. “They have responded to us. And me and Ronnie have done a better job of responding to them and what they are doing up front. It just took some time.”

The ability to run is a staple of Kubiak’s offense. It sets up play-action passes, creates open crossing routes for tight ends and tames defenders. When the Broncos run the ball at least 25 times this season, they are 9-1.

“Everyone just has a better feel for what we are trying to do,” said tight end Owen Daniels. “C.J. and Ronnie have been seeing the holes awesome and cutting things back and making things happen when they aren’t there. That’s what you want. They are running hard and with a purpose. Being able to run in the playoffs is huge.”

It can’t be overstated how much this helps the Broncos in pass protection, preventing even an aggressive Steelers front from pinning its ears back.

“Anytime you’re playing in the playoffs, you’re playing against the best,” said offensive tackle Ryan Harris. “They’ve got some of the best defensive front that’s out there in football right now. We’ve just got to execute our game plan. Really for us, it’s all about us and what we do. We’re focused on that right now. We want to contribute and do our part.”

Of course, issues remain. Michael Schofield, who could start Sunday’s game at right tackle despite being benched in the regular-season finale, has struggled in pass protection. Schofield used the bye week “to work on technique and get my confidence back.” Tyler Polumbus figures to get snaps at right tackle. Experienced guards Louis Vasquez and Evan Mathis are sharing the workload as rookie Max Garcia plays the majority of the snaps. This wasn’t the plan coming into the season. But the Broncos lost two left tackles, Ryan Clady and Ty Sambrailo, to injuries. Vasquez and Mathis have dealt with injuries too.

The mistakes, as such, have been amplified. And come Sunday, there is little margin for error. A hard sack of Peyton Manning could change everything, given his age (39) and Brock Osweiler’s injured right knee.

“We go into the game knowing we never want the quarterback to get his jersey dirty. That’s the goal,” Paradis said. “Peyton’s done this for a long time. We need to do our job. Of course, it’s personal.”

Troy E. Renck: trenck@denverpost.com or @troyrenck

Evolution of the Broncos’ offensive line

The Broncos’ offensive line underwent an extreme makeover this season because of injuries and defections in free agency. A look at how the playing time shook out during the regular season, reflecting the constantly evolving group: