The 49ers could start the season with three former first-round picks on their four-man defensive line.
The exception? Nose tackle Earl Mitchell, a former third-round selection who went largely unnoticed when San Francisco was going through non-contact practices in the spring but who jumped out as soon as the pads went on earlier this week.
Coaches this summer must pick a starting center between Daniel Kilgore and Jeremy Zuttah. So far both have had a hard time blocking Mitchell, especially in one-on-one pass-rush drills.
"He's not huge, but he's quick off the ball," Zuttah said. "… Just him being able to get into you before you're set is an advantage for him."
Nose tackles typically are massive players who enter games for run support but who waddle off in obvious passing situations. Last year the 49ers' nose tackles played about 45 percent of the team's defensive snaps.
Weighing 310 pounds, Mitchell is a more nimble, more relentless version of the archetype, and he is making a case to remain on the field -- or at least be part of the rotation -- when the 49ers switch into their nickel defense.
"Earl is exactly what we thought he’d be," defensive coordinator Robert Saleh said Wednesday. "Plays his butt off, works hard, is very strong, and is very hard to block. Everyone’s going to get a chance to rush the passer. We’re a defense where we’re in a mindset that we want fresh bodies rotating at all times throughout the game. You might see him in there rushing the passer every once in a while, but we’re hoping that by the end of training camp and preseason we can come at them in waves.”
The 49ers signed Mitchell as a free agent before the official free-agency period even began in March.
After he was released by the Miami Dolphins in February, four teams -- the Seahawks, Falcons and Broncos were the others -- tried to land Mitchell. The 49ers outbid them with a four-year, $16 million deal.
For one, Mitchell was familiar to position coach Jeff Zgonina, who was an assistant with the Houston Texans in 2013, a season in which Mitchell finished with a career-best 87 tackles for the Texans.
"He played the position for 17 years," Mitchell said of Zgonina. "He really helped me understand blocking schemes. He really elevated my game playing in this scheme. Fast forward to coming here, and it's basically that we're able to continue what we worked on in the past."
Perhaps more important, the 49ers run defense not only finished last in the NFL in 2016 in yards and rushing touchdowns allowed, but set a franchise record in giving up 166 yards per game on the ground.
The 49ers declined to re-sign one nose tackle from a year ago, Glenn Dorsey, and cut another, Mike Purcell, in May.
That means that Mitchell, 29, is the senior member of San Francisco's interior defensive line. He said he's usually "a quiet guy" but has been busy this summer giving advice to younger teammates like Arik Armstead, Deforest Buckner and 2017 rookies Solomon Thomas and D.J. Jones.
His biggest tip involves hustle: Always make sure you're running to the ball.
"I let them know it's a way for them to either make the team or stand out on film," Mitchell said. "It's a way to get the stats up. It's just kind of something I live by. It's a standard I hold myself to."