After visiting with the Seattle Seahawks earlier in the week, free-agent defensive tackle Earl Mitchell will arrive in the Bay Area Tuesday and meet with the 49ers through Wednesday, a source said.
Mitchell, 29, got a head start on free agency when the Dolphins released him last week, and he has four teams interested. After the 49ers, he will head to Denver before winding up his tour in Atlanta.
The 49ers, Seahawks and Falcons all run a similar scheme, which has been described as a 4-3 defense that utilizes personnel that also would fit a 3-4 defense. For the 49ers, one of the missing elements for such a defense is big-bodied defensive tackle adept at stopping the run. Mitchell is listed at 6-3, 310 pounds.
San Francisco's top interior defensive lineman, Glenn Dorsey, will be a free agent next month and the 49ers have not been eager to re-sign him after he's missed big chunks of recent seasons with a torn biceps and an ACL injury. Quinton Dial and Mike Purcell are other options, but neither is perfectly suited for the role.
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The Seahawks and Falcons also may have to replace soon-to-be free agents in the middle of their defensive line -- Tony McDaniel in Seattle and Jonathan Babineaux in Atlanta. Mitchell is familiar to the 49ers' new defensive line coach, Jeff Zgonina, who served as an assistant defensive line coach in Houston in 2013 when Mitchell was with the Texans.
The 49ers last week officially replaced Jim O'Neil with Robert Saleh as defensive coordinator. Saleh spent time on the Seahawks defense staff before following one-time Seahawks defensive coordinator Gus Bradley to the Jaguars. Saleh, 38, served as Bradley's linebackers coach in Jacksonville.
In addition to a run-stuffing defensive tackle, the 49ers also could stand to add an elite pass rusher, another inside linebacker or two to provide depth and competition to NaVorro Bowman and Ray-Ray Armstrong and, depending on what position Jimmie Ward plays next season, a fast and rangy free safety in the mold of Seattle's Earl Thomas.