The 49ers have been grinding it out this season.

Through 14 games, San Francisco scored a league-high 139 points on drives that lasted 10 or more plays. It’s not the ideal situation for coach Kyle Shanahan, but he is learning to embrace this style of offense.

“We might not have quite the same speed we’ve had other years,” Shanahan said this week on “49ers Game Plan.” “So I don’t think we have as many long plays, as many explosives, as we’ve had in years past. But whatever we’ve lost with that, I think we replace with more consistency.

“I think we got some really good football players who know how to move the chains, who know how to stay on the field, and know how to get in the end zone.”

The 49ers (10-4) enter their game Monday night against the Indianapolis Colts on a four-game win streak. They remain in the mix for the top spot in the NFC West and the No. 1 seed in the NFC playoffs.

They will need to run the ball effectively and find a way to slow down the top rusher in the NFL in order to keep pace in the playoff picture.

Here are five 49ers who must step up in order for San Francisco to control its own destiny heading into Week 17:

C Jake Brendel

Although the 49ers have been unable to generate a consistent running game, center Jake Brendel has graded out as one of PFF’s top run-blocking centers.

Brendel has not surrendered a sack, but he has given up 20 pressures in 12 games. He will have his hands full on Monday night against one of the best defensive tackles in the league.

DeForest Buckner, who played his first four NFL seasons with the 49ers, is expected to be back in the lineup after missing five games with a neck injury.

Buckner will line up at right defensive tackle and left defensive tackle. Regardless, Brendel will be responsible for keeping the 49ers’ O-line on the same page and helping guards Spencer Burford and Dominick Puni against Buckner.

DE Bryce Huff

The 49ers acquired edge rusher Bryce Huff in an offseason trade with the Philadelphia Eagles to provide some support for Nick Bosa on the other side.

But once Bosa was lost for the season with a torn ACL, the 49ers needed Huff to step up and take charge. He really has not yet done that.

The 49ers sent a conditional fifth-round pick to the Eagles for Huff. If he registers eight or more sacks, the 49ers would instead send a fourth-rounder to Philadelphia.

Huff registered four sacks in his first seven games. He has not produced much since Oct. 19. The 49ers have a league-worst 16 sacks on the season, and some pressure falls on Huff to begin generating more consistent pressure.

WR Jauan Jennings

Jauan Jennings is healthy and playing at a high level. Since Week 9, Jennings’ six touchdown receptions is tied for second-best in the NFL.

Starting wide receiver Ricky Pearsall is out with ankle and knee injuries, so there is little question that Jennings will attract the most attention from the Colts’ secondary.

Indianapolis opened the week with the league’s 31st-ranked pass defense. The Colts surrendered an average of 247.6 passing yards per game through 14 games.

The 49ers have the second-ranked third-down offense with a conversion rate of 49.2 percent. That is an area of the game that Jennings excels, living up to his moniker of Third and Jauan.

S Malik Mustapha

Second-year safety Malik Mustapha will play a vital role Monday night. He likely will play close to the line of scrimmage with his sights set on Colts running back Jonathan Taylor.

Taylor entered the week with a league-leading 1,443 yards and 16 touchdowns on the ground. The 49ers’ run defense has not been a strength, so San Francisco will have to stack the box and focus on slowing down Taylor.

That is not the only challenge for Mustapha. He also must be on high alert against 44-year-old quarterback Philip Rivers.

Rivers does not have the arm to take deep drops and drive the ball into tight windows. Mustapha will be challenged to take away some of Rivers’ quick underneath throws while also being on guard for the occasional pass down the field.

QB Brock Purdy

The last time Brock Purdy made an appearance on “Monday Night Football,” it did not go well.

Purdy threw three interceptions in the first half against the Carolina Panthers on Nov. 24, and the hot-take crowd tried to convince themselves that Purdy should be benched in favor of Mac Jones.

Purdy has bounced back while playing a key role in the 49ers’ win streak. Over the past 10 quarters, Purdy has completed 48 of 68 (70.6 percent) for 542 yards with four touchdowns, no interceptions and a passer rating of 113.7.

While Rivers will be the big storyline in this game, Purdy also will be the subject of much talk as he looks to play the kind of football expected from a man who signed a $265 million contract in the offseason.

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