Brown is starting because the 49ers lost Talanoa Hufanga to a season-ending ACL injury. If Brown can't play, recently-signed veteran Logan Ryan will take his place alongside Tashaun Gipson.
"It's a knee sprain, and there's timelines on that, but those are just that, timelines," general manager John Lynch told Guy Haberman and John Dickinson Friday morning on Bay Area radio station KNBR. "And Ji'Ayir is eager. He's young, so he heals quickly. And it's one of those [things] that's going to go right down to the wire. I know he wants to play. He's been out moving around. We'll see if he can make it.
"If not, [S] Logan [Ryan] will fill in, and we feel very confident that he'll do a really good. A number of our injuries this week are going to be kind of going right down to the wire."
Lynch praised Brown's character and toughness, which was evident in his performance against the Ravens.
"I mean, he injured his knee in the first quarter of that game versus Baltimore, played the entire game," Lynch explained. "And then we find out that he's got an injury. And so you appreciate who he is, what he represents, and the way he's been playing.
"Unfortunately, there's patterns that happen in this league, and it seems that injuries kind of happen in bunches to certain position groups. It started with Hufanga. [S] George Odum then went down. And then Ji'Ayir comes in and is settling in and doing really well."
"Thank God, Tashaun Gipson, he's stayed healthy and kind of held it down back there, but we had to start looking for some depth."
This prompted the 49ers to sign Ryan, who is in his 11th NFL season. Though he has only played 12 defensive snaps since joining the team, Ryan may assume a more significant role on Sunday if Brown is unavailable.
"And it's nice when there's a vet like Logan Ryan out there," Lynch commented on the signing. "... And Logan, it's nice to have a guy [who's] got a lot of versatility to his game, has played some nickel over the years for championship teams in New England. [He] was last in Tampa and was playing at a high level; played well against us when we last played them [last year].
"So, Logan, it's nice that if Ji'Ayir can't go, that you can turn to a guy like Logan Ryan and feel very comfortable with what you have back there."
You can listen to the entire conversation with Lynch below.
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