NaVorro Bowman and Patrick Willis are the standard when it comes to punishing play at inside linebacker, and their bond is a remarkably close one, driving each of them to reach for new heights -- even this year, with the All-Pro selection Bowman expected to be out until roughly midseason in his quest to come back from the grisly torn ACL and MCL he suffered against the Seahawks on one of the NFC title game’s most dramatic plays.

OWINGS MILLS, Md. -- They were easily the NFL’s premier inside linebacker tandem the past three years, the glamor and guts of a stellar 49ers defense that has finished among the league’s top five in each of those seasons. But the way Patrick Willis sees it, things will never be the same for him and NaVorro Bowman once Bowman returns from the devastating knee injury he suffered in the second half of San Francisco’s narrow loss at Seattle in last January’s NFC Championship Game.

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​"I told NaVorro today -- and I didn’t plan on [saying] this now -- but I told him today, I said, 'Man, when you’re back, if they think they saw something before,' I said, 'We are going to be the best two middle linebackers that have played the game, together and individually,'" Willis said this week after a 49ers-Ravens joint practice session at Baltimore’s training camp. "I just really felt that. When he gets back, it’s going to be even better than it was."

That’s setting the bar of expectation on its highest possible rung, but Bowman and Willis are the standard when it comes to punishing play at inside linebacker, and their bond is a remarkably close one, driving each of them to reach for new heights -- even this year, with the All-Pro selection Bowman expected to be out until roughly midseason in his quest to come back from the grisly torn ACL and MCL he suffered against the Seahawks on one of the NFC title game’s most dramatic plays.

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Willis acutely feels the absence of his friend and fellow playmaking linebacker during this year’s training camp, but Bowman has remained as close to the action as possible, motivating his teammates and himself as he works his way back from reconstructive surgery in February.

"He’s still been coming out to practices, he still comes to meetings," Willis said of Bowman. "But it’s nowhere near the same as spilling sweat together or looking over at him and he’s there and you’re thinking to yourself, 'Hey, let’s go. We’ve got to make a play, we’ve got to dig down.' There’s just something about grinding through camp with your close friend. He’s like a brother to me, and I do miss him. I won’t lie. But I also understand that you still have to go out and perform and play my best without him being there."

From the sideline, Bowman continues to see the game from an inside linebacker’s vantage point, and he has not been shy about sharing his insights with Willis, who preceded him in the NFL by three years.

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"He’s there watching me and coaching me," Willis said. "There are times where I have a play and I’m coming to the sidelines and he’ll be like, 'Hey, Pat, on that one you’ve got to go here.' And I’m like, 'Gotcha, gotcha, gotcha.' Or I’ll do something and he’s looking at me and he’s got a smile on his face, and I’m like, 'I know man, I should have been sitting a little tighter there, huh?' And he’s like, 'Yep, yep.' So he’s not out there, but he’s still here in my ear at times."

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And in his head. Like many 49ers, Willis can’t quite shake the ghastly scene that was Bowman’s fourth-quarter knee injury. Bowman stripped the ball from Seattle receiver Jermaine Kearse inside San Francisco’s five-yard line, only to have his left leg bent grotesquely inward and his recovery of the ball negated when game officials incorrectly ruled the Seahawks had possession. The NFL this offseason changed the rules to allow the recovery of a loose ball in the field of play to be reviewed by replay, the so-called "NaVorro Bowman Rule." Not that it restored San Francisco’s best defender to its lineup without him first undergoing a grueling rehabilitation.

"I was watching some film the other day, and actually they were showing the new NFL rules, and I saw it again," Willis said. "I still remember that play like it was yesterday. It was just one of those times where it almost felt like things went into slow motion. It wasn’t a good feeling.

"But his spirits are high, and he’s doing good. Every day he shows me something new that he can do, something that he couldn’t do yesterday. It’s almost like being able to tell your sibling or your best friend something new that you just learned. I just tell him, 'Good job, man. Keep working. Keep it up.'"

Bowman, 26, almost certainly will begin his fifth NFL season on the 49ers’ physically unable to perform list, meaning he’ll be ineligible to play until Week 7 in the best-case scenario. Until then, San Francisco’s defense is waging a camp competition between third-year veteran Michael Wilhoite and third-round rookie Chris Borland for Bowman’s spot in the starting lineup. Wilhoite has the edge in experience, even starting two games last season in place of the injured Willis. But Borland, an undersized but energetic playmaking force from the University of Wisconsin, has clearly captivated 49ers coaches and Willis with his contact-seeking style of play.

"He’s a little pit bull," Bowman said of the 5-11, 248-pound Borland. "I love watching him play. He reminds me a lot of NaVorro. [He plays] real low and compact. It seems like they never break stride. They’re always moving and they always get to the ball."

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Willis acknowledged his familiarity level is much higher with Wilhoite because the two have practiced together the past two seasons. But the similarity between Borland and Bowman’s game can’t be underestimated, Willis said.

"They’re both going to take some chances, but they’re going to make some plays from taking those chances," Willis said. "Whereas I’m a little more conservative, a little more read and react, and more of a safety valve, they’re more like, 'I’m going to go for it, and you back me up.' But whatever works. I say as long as you’re gambling and you win more than you lose, I don’t have a problem with that."

With Bowman out, Willis was expected to switch to the "Mike" inside linebacker position that Bowman has filled the past three years, as opposed to the "Jack" slot Willis has manned, with more coverage and pass-rush responsibilities. But that plan could change depending on who earns the other starting job. If it’s Borland, Willis will stay at "Jack" with the rookie handling the "Mike" role. With Wilhoite in the lineup, he’d be at "Jack" and Willis would serve as "Mike."

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"Whatever is going to be best for the defense is whatever [defensive coordinator] Vic [Fangio] decides," said Willis, who has made the NFC Pro Bowl team in all seven of his NFL seasons and been named All-Pro five times. "I’m going to play my very best at either/or. Right now, I’m preparing to play the 'Mike,' but if it happens I have to go back to 'Jack,' that’s where I’ve played these last three years, so I can hold it down there. A lot of people forget my first four years in the league I played similar to the 'Mike' in our nickel defense."

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Replacing Bowman, of course, is far from the only challenge the 49ers defense will face in the season’s first half, even if it is the most daunting. The team’s most dominant pass-rushing threat, outside linebacker Aldon Smith, is reportedly facing a six- to eight-game league suspension for a string of off-field incidents that violated the NFL’s personal conduct policy. Smith missed five games last season while enrolled in a substance abuse counseling program, and during that span the 49ers went 5-0 and eventually wound up playing in their third consecutive NFC title game. But San Francisco had both Bowman and Willis on the field while Smith was out. The defense recently encountered another obstacle in camp when defensive tackle Glenn Dorsey suffered a torn biceps, which could be a season-ending injury. In addition, nose tackle Ian Williams (ankle) and defensive end Justin Smith (shoulder) are rehabilitating injuries.

"If something is to happen and we are without Aldon for a little while, then someone else will have to step up, as they did last year when he was out," Willis said. "And same goes until NaVorro gets back. But my role will still be the same it always has been. I don’t try to put any more stress on myself than what I already put on myself, trying to be the very best I can be. That’s why you play team defense, and we all have to find a way to pull together and make it work."

With the 49ers falling just shy of a Super Bowl ring in each of the first three years of Jim Harbaugh's time in San Francisco -- two NFC Championship Game losses and a Super Bowl loss -- a now-or-never sense of urgency could prevail in San Francisco this season. Willis said he’s ready for that challenge.

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"It’s kind of a cliche, but I honestly feel like I’m young again," said Willis, only 29 but entering his eighth NFL season. "I mean, my body feels good and my weight [240] is good. People keep saying, 'Man, you look really skinny.' But I’m actually still close to the same weight, it’s just my diet and eating habits have changed. I’m disciplined on how I take care of my body and I really feel good. And when NaVorro gets back, we’re going to show people we’re even better than we were before."

The rest of the NFC can’t be overly excited to hear those prospects. Even the 49ers' nearly week-long trip to the Baltimore area this preseason served its purpose, if only to remind San Francisco how close it came to reaching the NFL’s mountaintop in that agonizing Super Bowl loss to the Ravens in February 2013.

"I would be lying if I said I didn’t think about it a couple of times," said Willis, talking to reporters at the Ravens team complex. "I can be sitting at home and NFL Network starts showing clips and you can see that game, or we’ll be watching film and coach (Fangio) will have some plays from that game up there. I’ll just look at NaVorro and say, 'Wow, that was us. We were in that game.'

"I told NaVarro, 'We’ve got to get back there. And if we get back, we’re bringing it home.' That’s the hunger. That what you fight for every year. And that’s what we’re going back after this year."

For now, the final stages of a recovery from serious injury and the highs and lows of another long, arduous season await. Willis and Bowman are both driven to get all the way back, and when they do, they don’t want things to be the same as before. Being the best ever is the goal.