Count San Francisco 49ers defensive coordinator Robert Saleh among those who came away viewing rookie linebacker Fred Warner as one of the many bright spots during the team's Week 1 loss. While Warner's physical talents were on display Sunday, Saleh says the linebacker's study habits off the field are also an asset.

"He's a film junkie," Saleh told reporters before Thursday's practice. "That's what he was coming out of BYU. You see him eating breakfast and watching tape. He's sitting at a table by himself in the cafeteria, and he's got the tape rolling. He's always deep in the film, and if he continues to progress the way he is, he does have a bright future. But like I said, consistency is the truest measure of performance, and he's got to consistently do it."

Warner was credited with 12 combined tackles, a pass defensed, and a forced fumble while playing in every defensive snap against the Minnesota Vikings. What did Saleh think of the linebacker's first NFL start?

"I thought he had good command in the huddle," he said. "He did a really good job relaying the calls, did a great job getting people lined up. He made plays when they were presented to him, saw the game very well. He did have mistakes, some that are not seen to the naked eye, so he's got a lot of stuff that he does have to clean up.

"Statistically, obviously, he produced and made a lot of plays, but he'll tell you himself that there's a lot of room to get better."

Head coach Kyle Shanahan already stated that, if Warner continues to play like he did against the Vikings, it would be tough to get him off the football field once Reuben Foster returns and Malcolm Smith gets healthy.

Foster will return to practice next week after serving a league-issued two-game suspension. Fans have to be excited about the prospect of seeing Foster and Warner on the field at the same time.

Saleh didn't want to speculate on what might happen next week. Instead, he is focused on the 49ers' next opponent — the Detroit Lions. Warner is slated to make his second start at the MIKE linebacker spot.

"He has to go prove it again, Fred does," Saleh said. "If he continues to play at that level, yeah, it would be hard (to get him off the field). But in the NFL, you can have a great game and the very next week become nothing all over again. He's got to go out and show that consistency over and over again."

Cornerback Richard Sherman also spoke to the media on Thursday and was asked about his young defensive teammate.

"He did a good job," Sherman said of Warner. "He did a really good job. He was calm. He was poised. If you didn't know he was a rookie, you would have never guessed he was a rookie. He was deliberate, made a lot of great tackles. Obviously, the forced fumble (which Sherman recovered) was a huge play. But he got his hands on multiple footballs, got a QB hit. I mean, he was all over the place."

Sherman may not notice Warner's study habits like Saleh does, but the veteran cornerback can see the results on the field.

"You can see he's always in the right spot," Sherman said. "He recognizes plays really fast. He diagnoses things. He gets to his spots. So those are things that you can see he really puts the work in (to study), puts the time in."