Kurtenbach: The 49ers need to trade for a defensive difference-maker. Here are their three best options

The San Francisco 49ers have needs in many places ahead of Tuesday’s NFL trade deadline, but nowhere on the roster is the need more pressing than defensive tackle.

The team has a downright mediocre run defense, and while that is a byproduct of the entire defense’s play, the defensive tackles carry the heaviest load against the rush.

And while the Niners might have plenty of bodies at the position, they lack impact options up the middle.

In particular, they’re lacking someone who can hold a gap.

So, yes, the Niners should be looking to add a pass rusher, a weak-side linebacker, a true free safety, an X wide receiver, and a No. 2 tight end (amongst other things), but they should be first and foremost be looking to add a big fella up the middle.

Stop the run, and this Niners’ defense has a chance to be not just good but great.

But who should that big fella be?

I have three realistic, prudent names for you:

Calais Campbell – Miami Dolphins

Campbell, 38, has been in the league seemingly forever. That’s no accident. Because even after 17 years, he can still make winning plays.

Per Pro Football Focus, the 6-foot-8 behemoth is still one of the finest run stuffers in the NFL — ranked fourth in the league. This, on a defense that is, in so many words, a hot mess.

The Dolphins are 2-6. They’re not making the playoffs. Campbell has six Pro Bowls, three All-Pro selections, and more than 100 sacks. He doesn’t have a Super Bowl win, though. The Dolphins owe it to him — if he’s interested, of course — to trade him to a team with a chance to win one.

The 4-4 Niners might not seem like that team right now, but the oddsmakers (of the algorithms that pretend to be oddsmakers) still have San Francisco with the fourth-best odds to win it all, at least before this weekend.

And adding a behemoth who can hold up offensive linemen from getting to the second level — a giant who can plug a massive hole in the middle of the Niners’ defensive line — would help those odds.

Better yet, it’d cost next to nothing to acquire him. A late Day 3 pick in the upcoming draft, or next, would be ample compensation for the Dolphins, who would be rewarded mainly by doing the right thing for a legend.

Fiscally, Campbell is playing on a discount contract with the Dolphins, and the Niners have more than $50 million in cap space, though almost all of it is earmarked to be rolled into next season so that the Niners can sign Brock Purdy to a massive contract extension.

Shelby Harris – Cleveland Browns

Harris, 33, is another run-stuffing big man, like Campbell, who is on a favorable contract ($1.25 base salary for 2025) and is yet to sniff a Super Bowl in his career.

The Browns are cooked, but Harris is not. He’s still a space-filler of the highest order.

It should be noted that the Niners’ defensive line scheme — the fabled Wide Nine — asks linemen, even interior ones, to shoot gaps in an effort to be in the backfield. The problem with that is that such tactics are hit-and-miss. Far too often this season, it’s been miss, with Niners interior defenders being swung open like doors, creating easy running lanes.

The Niners need someone to hold that door shut.

Conceptually, a Campbell or Harris might not fit with what the Niners want to do. They don’t burst into the backfield off the snap.

But I’m betting that landing someone who can stand in the middle and not move — even against double-teams — would be a win for the Niners’ defensive line. Harris, a veteran on a team that’s going nowhere (Cleveland is 2-7) would be an exceptional candidate for the gig.

Jeremiah Ledbetter – Jacksonville Jaguars

Defensive tackle isn’t the flashiest position, but I bet you knew Campbell and perhaps even Harris.

I’ll give you a moment to look up Ledbetter.

Suffice it to say, he’s not a sexy player, but he’s the exact kind of defensive tackle the 49ers need.

His game, in a word: tree.

As in he is as hard to move as a big, deep-rooted tree.

One man, two men, three — Ledbetter holds his position better than almost anyone I’ve seen in the NFL. This man, unlike the Niners’ interior offensive linemen, anchors.

And he’s cheap. The Jags are another team that should be selling off ahead of Tuesday’s trade deadline, but they’re not in a position to start a full rebuild — they spent a lot of money in free agency the past few seasons; they’re pot-committed.

But landing something — a late Day 3 pick, most likely — for a 30-year-old depth defensive tackle in the final year of his current contract? That would be smart business.

So it might not seem appropriate, but the Niners need to get former GM Trent Baalke on the phone and land Ledbetter.

He might be unknown, but his impact in the run game for San Francisco would be quite obvious.