SANTA CLARA -- Patrick Willis and NaVorro Bowman still sit next to each other during team meetings. They still swap notes about the nuances of playing linebacker and they still push each other in the weight room.
But when it comes time to take the field, Willis does so alone. A torn ACL will keep Bowman sidelined about half the season, reducing the 49ers' celebrated inside linebacker tandem to a solo act.
Willis said Tuesday that his tag-team partner's absence is made tolerable this week only because of the low-key nature of OTAs. But Willis already dreads the day when he must make it through a sweltering training camp practice without Bowman by his side.
"When you need a little motivation, sometimes you can look to the guy next to you and say, 'Well, if he's going through it, if he's getting better, then so can I,' '' Willis said. "I'm most definitely going to miss that."
The 49ers will miss Bowman, too. The third-year linebacker was coming off a career-best season and his third consecutive first-team All-Pro selection.
How will the 49ers replace him? Michael Wilhoite, 27, who performed well in spot duty last season, is the front-runner. Other candidates include second-year player Nick Moody as well as rookies Chris Borland (third-round pick from Wisconsin) and Shane Skov (undrafted out of Stanford).
In at least some ways, though, the man to replace Bowman will be Willis.
The seven-time Pro Bowler said that coaches recently approached him about taking on the duties that belonged to Bowman. Though both players are listed as inside linebackers, there are subtle differences in their job descriptions. Willis plays a traditional "mike" (middle) linebacker while Bowman plays the 49ers' version of the "jack" (a hybrid spot for someone comfortable in coverage and rushing the QB).
Willis said Tuesday the "jack" role is similar to what he played for four years under former 49ers defensive coordinator Greg Manusky.
"Since the day we put in the defense, I always take pride in knowing what all other 10 guys do, not just my position,'' Willis said. "So when coach came to me and asked me, it was one of those things where I know it, even though I haven't played a lot of it.
"There's not a whole lot of difference. You just tend to be a little more in the mix in terms of the (opponents') offensive strength. I think that's probably the biggest difference. But it's not a life-threatening difference."
Willis, the face of the defense, found himself giving something of a State of the Linebackers address Tuesday. Besides missing Bowman, the 49ers face the prospect of playing without sack leader Aldon Smith in the wake of his legal trouble.
Smith recently pleaded no contest to three felony charges of possessing illegal assault rifles and misdemeanor DUI, stemming from separate incidents in 2012 and 2013. The NFL could come down hard on Smith considering that alcohol and guns are two of the league's hot-button issues.
Willis said the 49ers aren't caught up in a potential suspension.
"For us, it's not something we worry about,'' Willis said when asked about Smith. "He's out here working. ... He's been a great teammate. That's our focus right now: Worrying about the present.
"If he's not out here, then just like last year, some of the guys will have to step into his place and play big time. We'll see when that time comes."
Follow Daniel Brown on Twitter at twitter.com/mercbrownie.
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