SANTA CLARA – You’re starting to see how improved the 49ers run defense is, right? Statistics illustrate that. Quotes provide testimony. Victories reassure that.

A better question: Why are the 49ers better at stopping the run?

“I really think it’s just a trust level on defense amongst the guys,” defensive tackle DeForest Buckner said. “Trusting everybody is going to be in their own gap doing their job.”

If the 49ers (3-10) are to pull off their third straight win, their run defense needs to stifle the Tennessee Titans (8-5) and the league’s 10th-best ground attack. That will help get the ball back to Jimmy Garoppolo in his home debut as the 49ers starting quarterback, a method that’s paid off in back-to-back wins.

“On the sideline, there’s energy that’s being fed to the (49ers) defense, and the urgency that they feel the need to get the (49ers) offense the ball,” defensive coordinator Robert Saleh said. “It’s verbalized by those guys. You’re starting to see the team rally around each other.”

Before hyperbolizing the 49ers run defense’s strides, keep in mind only seven teams are allowing more rushing yards. Plus, any improvement looks magnified compared to last season, when the 49ers allowed their most-ever rushing yards and rushing touchdowns. To wit:

— Rushing yards per game: 165.9 last season; 121.3 this season.

— Rushing touchdowns: 25 last season; 10 this season.

— 100-yard rushers: 11 last season; three this season.

— Yards per carry: 4.8 last season; 3.9 this season.

That yards-per-carry average ranks seventh-best in the league. “If you’re under 4 yards a carry, throughout the recent history of this league, you should be in the top 10,” Saleh said.

Saleh’s No. 1 priority this season was to stop the run – no surprise there – and he altered the scheme to single-gap assignments.

“He showed clips of last year, of what went well and what didn’t go well,” Buckner said. “Most of the guys aren’t here anymore.”

Reuben Foster and Brock Coyle are forming a nice linebacker duo. Veteran Earl Mitchell is plugging away at nose tackle. Top draft pick Solomon Thomas is adding versatility next to Buckner and a rotating cast.

“It was embarrassing last year being 32nd in the league in the run,” Buckner said.

That defense got bulldozed Oct. 22 by the Dallas Cowboys, who had 43 carries for 265 yards in a 40-10 rout.

“That was a tough game for us,” Reid said. “We knew we couldn’t let that happen to our team, that if we were going to win games, we have to do our part.”

Reid said the Titans are “by far” one of the league’s best rushing teams and the 49ers must not stray from their assignments.

“They have a large, probably the biggest, run-game playbook I’ve seen on tape,” Saleh said. “They come out at you many different ways.

“This is going to be a great game with regards to locking in on your keys, trusting your fundamentals, being great with your eyes and understanding your responsibility,” Saleh added.

The Titans’ 17 rushing touchdowns are second only to the New Orleans Saints (19). Five touchdowns apiece have come from running backs Derrick Henry (649 yards) and DeMarco Murray (552 yards) as well as quarterback Marcus Mariota (224 yards).

“We felt good throughout the entire year,” Saleh said. “There were a couple lame ducks in there – the Dallas game still punches me in the stomach. But the overall structure of the defense, we don’t feel we’ve been schemed at all and we feel very sound.”

Related Articles 49ers on Wednesday: Garoppolo likely to miss game vs. Giants; a healthy RB has impressed

49ers bring in two former top-five picks to replace Nick Bosa, Solomon Thomas

The Deets: The 49ers’ big long-term challenge has arrived before anyone expected

No reinforcements: 49ers’ Dee Ford will miss at least another game, per report

Focus on New York Giants: Battered 49ers get another injury break — Right tackle Trent Brown’s season could be over if the 49ers ship him to injured reserve with a shoulder injury. He’s missed practice this week and two of the past three games. He hasn’t been seen during the media’s locker room access this week.

Zane Beadles started last game in place of Brown, and center Daniel Kilgore vouched for Beadles’ knowledge of assignments going forward, if need be.

— Cornerback Greg Mabin earned more playing time after relieving Dontae Johnson on Sunday, and both are expected to see action Sunday, Saleh said. Ahkello Witherspoon has been limited in practice with a knee injury, and Mabin showed up on Thursday’s injury report with being limited by a calf issue.

— Since being replaced by Garoppolo, backup quarterback C.J. Beathard said he’s prepared like usual, although his reps now have come on the scout team, where this week he’s impersonating Marcus Mariota. Beathard is a Franklin, Tennessee native and attended a couple Titans game each year, but he grew up a fan of the Chargers, where his grandfather, Bobby, served as general manager.

— Buckner and Mitchell, for the second straight week, got Thursday off to rest.