"He definitely won't play this week," Shanahan said. "You know, the good news is, he's not going to need surgery, so it will heal on its own. But, he's definitely not going to play this week. I'd be surprised, it's probably going to be a little bit longer than that, also."
Reid suffered the non-contact injury while in coverage with 4:39 left in the second quarter against the Seattle Seahawks. He remained seated on the turf of CenturyLink field before being assisted to the sideline and then heading to the locker room. Reid returned to the sideline prior to the end of the first half, thinking that he felt good enough to return to the game, but the trainers insisted he returned to the locker room for X-rays.
Reid returned to the game with just under 12 minutes remaining in the third quarter and was in for four plays before exiting again. With just 6:59 left in the same quarter, he once again went down without contact and remained kneeling on the turf before walking off to the sideline with the training staff. Reid did not return to the game.
Shanahan was asked why Reid returned to the game multiple times.
"They didn't feel that there was anything torn, so he felt it was alright," Shanahan said. "I haven't gotten to talk to him personally yet, so I'm not exactly sure. But, when he checked out, it seemed alright. The X-ray they had looked good, and he said he could go so he kept trying to go and then he had his final straw and said he couldn't go anymore. I guess that's what happened."
On Sunday, Reid said that he didn't initially believe the injury was that bad.
Reid has impressed the coaching staff throughout training camp, preseason, and the start of the regular season. He has been the 49ers' starting strong safety in both games this season and registered 12 tackles while showing off his versatility.
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"I think my cleat got stuck in the turf," Reid said. "I hate turf. My knee kind of wiggled. So I'm hoping it's just a sprain or something."
Reid was replaced in Sunday's game by Jimmie Ward, who was active for his first game this season – including preseason – after suffering a hamstring injury at the start of training camp. In his 2017 debut, Ward had five tackles and a pass defensed. Ward was limited during Monday's practice as the 49ers continue to be careful with his hamstring injury.
While Ward was limited, safety Jaquiski Tartt did not practice on Monday and Shanahan said that he was questionable to play against the Rams, which complicates the team's safety situation further.
The 49ers have a short week and will host the Los Angeles Rams on Thursday night at Levi's Stadium. The next game after that will not be until October 1 when they travel to Glendale, Arizona to face the Cardinals.
"He's playing that role that we've seen Kam Chancellor play so well," Lynch said. "And Eric's probably not the physical player that Kam Chancellor is but he's a better athlete, I believe."
Over his career, Reid has 263 total tackles, a sack, 30 passes defensed, and two forced fumbles. The 49ers made him the 18th overall draft pick in 2013.
