San Francisco 49ers' 2018 free agency: Jeremiah Attaochu could bolster pass rush

The 49ers are giving Jeremiah Attaochu an opportunity to prove that he's worth more than just a one-year deal. Scott Winters/ICON Sportswire

A breakdown of the San Francisco 49ers' 2018 free-agent signings.

Jeremiah Attaochu, DE

The 49ers signed Attaochu to a one-year deal worth up to $5.125 million on Thursday. Here’s a closer look at the defensive lineman who spent the previous four seasons with the Chargers:

Grade: B-minus. Attaochu has all the physical traits of a potentially capable "Leo" defensive end in the Niners’ scheme. He hasn’t produced much in his career, in part because of injury issues, but the upside is worth the minimal commitment.

What it means: The Niners addressed their most glaring need by adding Attaochu to help their edge-rushing efforts. After declining the option on Elvis Dumervil, the Niners needed serious help at the "Leo" spot. It’s unlikely Attaochu will be the cure-all there but without stars edge rushers like Joey Bosa and Melvin Ingram in front of him, he should at least get the chance to compete and could contribute on special teams as well.

What’s the risk: The risk is minimal since this is essentially a one-year “prove it” deal, giving Attaochu a chance to battle for a much bigger role than he had with the Chargers. Attaochu has dealt with injuries for most of his career, missing 14 games in his first three NFL seasons and then missing much of Los Angeles’ offseason program last year because of a hamstring ailment. Worst-case scenario: Attaochu struggles to stay healthy and offers no production at a position where the 49ers need it.

Jerick McKinnon, RB

The 49ers agreed with McKinnon on a four-year, $30 million deal Wednesday, according to ESPN's Adam Schefter. Here's a closer look:

Grade: C. This looks like an overpay for the 49ers, even though they will probably be able to get more out of McKinnon than he provided in Minnesota. Considering the way the 49ers generally structure their deals, we'll allow a little benefit of the doubt that this won't come in as shocking as it first appears.

What it means: This deal, combined with letting Carlos Hyde walk in free agency, sets McKinnon up to be the 49ers' primary running back. They clearly believe he was never able to maximize his potential in a role that never allowed him more than 159 carries in a season with the Vikings. One thing coach Kyle Shanahan will want from McKinnon is production as a receiver. Hyde struggled in that area last season and McKinnon is coming off career highs in receptions and receiving yards while missing only three "catchable" passes thrown his way, according to Pro Football Focus. Given Shanahan's track record of success with backs similar to McKinnon, he must have strong belief that this is a player with a lot more to offer than his previous numbers indicate.

What's the risk: McKinnon has never been the lead back in his four seasons and now the 49ers look to be paying him as one. As a runner, McKinnon has averaged 4.05 yards per carry and scored seven touchdowns, which doesn't inspire much confidence that he can be the primary runner. Even if the 49ers add another back capable of contributing from a deep draft class, that only raises more questions about what the 49ers are paying relative to McKinnon's role.

Weston Richburg, OL

The San Francisco 49ers agreed with offensive lineman Weston Richburg on a five-year deal Tuesday, according to ESPN’s Adam Schefter. Here’s a closer look at the move:

Grade: B. Richburg gives the Niners the type of athletic, versatile interior lineman who can operate in their offense without issue. Without knowing the contract terms, it’s hard to grade the deal but based on fit, this is a good match.

What it means: The Niners addressed another glaring need, this time on the interior of the offensive line. And they did so by finding a player who can provide two things coach Kyle Shanahan values most in an offensive lineman: athleticism to get to the second level and versatility. Richburg is probably best suited to center but can also play guard. The Niners will have to find his best fit after also re-signing center Daniel Kilgore, but they’ll take the approach of getting the five best linemen on the field to help protect quarterback Jimmy Garoppolo and spark the run game.

What's the risk: Richburg, 26, is coming off a concussion that cost him all but four games in 2017. It was the first time he missed time because to injury, but he told New York reporters that he’d been cleared after missing a few games and the Giants told him they needed his roster spot.

Richard Sherman, CB

The San Francisco 49ers agreed with cornerback Richard Sherman, who was drafted by the Seattle Seahawks in the fifth round of the 2011 draft, on a three-year deal worth up to $39.1 million Saturday. Here's a closer look at the signing:

Grade: B. The fit between Sherman and the 49ers is undeniable in terms of filling a need and the scheme. Concerns about how he returns from an Achilles injury are real, but the incentive-laden structure of the contract helps mitigate that risk.

What it means: The Niners have filled their biggest need, adding the most proven veteran cornerback on the market to a team that allowed a Total QBR of 87 last season, second worst in the NFL according to ESPN Stats & Info. In doing so, they also added a longtime rival who should serve as a mentor for a young defense in need of leadership. It's also worth noting that this move doesn't preclude the 49ers from adding at cornerback, and it appears they are all but certain to do so.

What's the risk: Sherman will turn 30 at the end of this month and is attempting a comeback from a torn right Achilles. He also recently had surgery to clean up bone spurs in his left heel. The 49ers and Sherman are each confident he'll be ready to go for training camp, but the real question is whether he can return to his previous Pro Bowl form for a defense that needs his production more than his leadership.