SANTA CLARA What would happen if both of the 49ers' Pro Bowl inside linebackers went down with injuries?
The team got a glimpse of that scenario during Wednesday's practice when Patrick Willis hurt his right hand, apparently during a pass-blocking drill, and NaVorro Bowman started but didn't finish the practice with an apparent groin injury. Bowman had missed Tuesday's session.
Backups Michael Wilhoite and Nate Stupar filled in, and Stupar had one of three interceptions on the afternoon when he jumped a Colin Kaepernick pass to Vernon Davis in the red zone.
Kaepernick and the offense had been winning the daily battles against the defense, but that was not the case Wednesday. Cornerbacks Nnamdi Asomugha and Chris Culliver also had interceptions, while Asomugha knocked away an end-zone pass from Kaepernick to Anquan Boldin, which to that point had been an unstoppable combination in training camp.
The 49ers' defense is special, of course, because it has two top-caliber inside linebackers who stay on the field for all three downs.
Neither Willis' nor Bowman's injury, however, appears too serious. If Willis suffered a fracture, he'll know what to expect. He's played with broken bones in his hand three times since college, including 2007, his rookie season, and 2010.
The defense rests? Defensive end Ray McDonald said the 49ers intend to do more rotating along the defensive line than they have in the previous two seasons when he's played as many as 91 percent of the team's defensive snaps.
Attrition appeared to be an issue last year with the unit, which sagged from mid-December through the playoffs.
"Yeah, that's the plan," McDonald said. "The younger guys are getting a lot more reps now. So we expect them to go in there and take a little load off of me and Justin (Smith). We do play a lot of snaps, so we've got to come out of there every once in a while."
The 49ers used draft picks on two defensive linemen, second-rounder Tank Carradine and fifth-rounder Quinton Dial. Both, however, have yet to practice. Carradine is recovering from ACL surgery and Dial had surgery to repair a torn ligament in a big toe.
Instead, the understudies along the defensive line have been Will Tukuafu at left defensive end and Demarcus Dobbs at right defensive end. Free-agent pickup Glenn Dorsey has been the second-string nose tackle behind Ian Williams.
Five defensive linemen typically suit up for a game. Others at the position include Tony Jerod-Eddie, who was on the practice squad last year, and rookie Lawrence Okoye, who could land on the practice squad this season.
Other injuries Culliver did not finish practice because of an apparent shoulder injury. Seventh-round pick Carter Bykowski, an offensive tackle, slowly walked off the field midway through practice and headed for the training room.