49ers open Yetur Gross-Matos' practice window

When asked why the team waited until Thursday instead of opening the window before Wednesday's practice, Shanahan explained, "Just because of how the whole offseason went with him, and our plan this year. We don't ever practice him two days in a row, Wednesday and Thursday, so he only practices on Thursdays, regardless, even before he got hurt. So we're not going to open until that day."

On Thursday, general manager John Lynch said it is "very realistic" to expect Gross-Matos to contribute in December.

"He ran into some knee issues throughout training camp, throughout the offseason," Lynch said during a radio interview. "Then, he kind of worked through those. We got him ready. He went out ... he was playing good football. Then he tweaked his hamstring, and then, when we were bringing him back in practice, re-tweaked that.

"And so, we've tried to give that the time that it needs so that he can come out and be impactful. Yetur, he's a physical specimen, a really good football player. It's been unfortunate because there's so much ability in there. His availability just hasn't been there. And so we're trying to make it such that he can be there for the stretch run."

The 49ers now have 21 days to evaluate Gross-Matos and decide whether to activate him from injured reserve.

"He's an excellent football player," Lynch continued. "He's a guy who can play outside, but then, is probably at his best when he moves inside on nickel or pass situations. He's a really effective football player."

Gross-Matos, now in his sixth NFL season and second with the 49ers, has recorded 165 tackles (25 for loss), 38 quarterback hits, 17 sacks, two passes defensed, two forced fumbles, and four fumble recoveries over his career.