49ers trying to find best use for Solomon Thomas, Arik Armstead

The 49ers saw late-season improvement from Solomon Thomas after moving him inside. Kelley L Cox/USA TODAY Sports

SANTA CLARA, Calif. -- As San Francisco 49ers coach Kyle Shanahan went about recruiting potential additions to his coaching staff, he offered most of the usual things that can be found in a coaching contract. Shanahan also threw out one extra carrot: the chance to avoid joining the current staff in coaching the Senior Bowl in Mobile, Alabama.

"That was part of my recruiting for them," Shanahan said, laughing. "I threw that out there before they said yes. If they'd have said yes, I would have never thrown that out there. I threw it out quick."

Jokes aside, Shanahan had more pressing issues in mind when he told new defensive line coach Kris Kocurek that he didn't have to go to Mobile. Namely, he wanted Kocurek to dive right into his new job by watching and evaluating the players he is about to coach for the first time.

As the 49ers head into free agency and the NFL draft, it's no secret they could use pass-rushing help. Specifically, the Niners would like to add a difference-making edge rusher to complement what they have at the other spots along the front four.

But before the Niners can figure out how potential free-agent signees or draftees might fit, they must first have a better understanding of how best to use the players already in place. For a team that has spent three of its past four top picks on defensive linemen, it's critical to understand the current players, what their upside might be and how Kocurek envisions using them.

That understanding will go a long way in shaping how the Niners approach free agency and the draft. At the top of the list of questions Kocurek & Co. must answer: Was Solomon Thomas’ late-season improvement after playing more inside a harbinger of things to come and where does he fit moving forward?

"I know that's going to be the big question," defensive coordinator Robert Saleh said. "Kris Kocurek is studying him, and we're going to sit down; I want his thoughts unbiased, so I'm not going to put anything out there right now. He kind of knows what we did. He knows what we did last year, and he knows what our thoughts are initially. But we're going to have him study, and we all want to see what he says and how he views him."

Thomas, the No. 3 overall pick in the 2017 draft, has struggled in his first two seasons. He has bounced around multiple positions along the defensive line, and he finished last season with just 31 tackles and a sack, though he seemed to find some traction late in the season when he finally bumped inside on a more consistent basis.

On the surface, simply moving Thomas inside from either end spot would be an easy solution, but it's not that simple. Three-technique defensive tackle DeForest Buckner is one of the team's best players, and Saleh is understandably hesitant to move him from that spot.

That has limited Thomas to moving inside in obvious passing situations while working on the outside on early downs. Complicating matters further is defensive end Arik Armstead, who was the team's primary "big" end in 2018. Armstead had his best and healthiest NFL season, particularly against the run. He finished with 48 tackles and three sacks while starting all 16 games for the first time in his career.

The 49ers also kicked Armstead inside to the nose tackle spot on occasion, lining him up next to Buckner in order to generate pressure up the middle. Under the fifth-year option, Armstead is due to count around $9 million against the 2019 salary cap. That's a hefty price given Armstead's injury history and production.

"We're working through that like a lot of other issues," general manager John Lynch said. "What I can say is Arik played some really good football for us. We were excited about the way he played, particularly at the end of last year. I think, much like [Thomas], he kind of found a place he was comfortable playing and really contributed at a high level for us.”

San Francisco already has parted ways with nose tackle Earl Mitchell this offseason. D.J. Jones is the obvious replacement for Mitchell, but the Niners also could try some other configurations that would see Armstead and Thomas essentially sharing the big end and nose tackle spots, depending on down and distance.

Once the 49ers have a better idea of where they want Thomas and Armstead, they can go about figuring out which additions make the most sense. There's little doubt that a "Leo" defensive end will be a need, but what if, for example, Alabama defensive tackle Quinnen Williams is clearly the best player available when the Niners pick at No. 2?

It's hard to imagine the Niners would draft Williams, since his best position is the one occupied by Buckner. But could Williams line up next to Buckner inside, providing the 49ers with a dominant interior rush? If so, what becomes of Armstead and/or Thomas? The trickle-down effect is real.

For now, there's only one thing the 49ers seem to know for sure when it comes to the defensive line: Buckner is entrenched as the 3-technique defensive tackle.

"I think DeFo could play all positions, but DeFo is an All-Pro 3-technique and removing him from that 3-technique spot, [the other player] would have to be damn good," Saleh said. "You can take a great 3-technique and move him over to 5 or nose, he is still going to be really good; but he's not going to be as good, so it's two spots [changed]. But Buck is phenomenal. He's one of the best 3-techniques in football, so we're trying not to mess that up."

The next step? Making everything around Buckner better.