SANTA CLARA -- When both Michael Wilhoite and rookie Chris Borland started last Thursday’s preseason opener at inside linebacker, it illustrated where things stand in the battle to replace NaVorro Bowman early in the season.
“Very even,” said defensive coordinator Vic Fangio on Wednesday of the competition at the position.
Patrick Willis, of course, will start at one of the inside linebacker spots against the Dallas Cowboys in Week 1. However, he was given the night off in Baltimore, which allowed Borland, a third-round draft pick, to play with the first-string defense. Willis also sat out Wednesday’s practice.
Both Willis and Borland have been playing the so-called “Mike” inside linebacker spot, which Bowman usually plays. Should Borland win the competition, it’s likely he’ll play “Mike” while Willis will move to the “Jack” spot, where he has played each of the last three seasons.
The positions are similar, although the “Mike” linebacker tends to be in a position to make more tackles while the “Jack” usually has more coverage duties.
Despite Fangio’s comments, it’s been Wilhoite, not Borland, who has lined up next to Willis with the first-string defense during practices this offseason. Because of that, he is still the frontrunner for the job.
Bowman, who is returning from a torn ACL, could be back in the lineup following the team’s Week 8 bye.
Reinforcements arrive – The 49ers’ presumed starting defensive line practiced together for the first time this season. Justin Smith is back from shoulder surgery, Ian Williams from a broken leg and Ray McDonald from a minor leg injury.
Several offensive players also took part in Wednesday’s session, including running back LaMichael James, who dislocated his elbow July 23. He practiced in a blue, “no-contact” jersey and with a brace on his right arm. But he returned kicks and also took several handoffs in team drills.
One veteran receiver, Brandon Lloyd, practiced in full. Another, Michael Crabtree, appears close to returning. He went through warmups and individual drills with the other receivers before stepping to a side field and working out on his own.
Costanzo shelved – Blake Costanzo, the charismatic captain of the 49ers’ coverage units in 2011, was placed on injured reserve. Costanzo, an inside linebacker, apparently got hurt in last Thursday’s game. The 49ers did not specify the injury.
Costanzo, 30, left for Chicago via free agency in 2012. The 49ers reacquired him in June.
The team filled his roster spot with another inside linebacker, Kion Wilson, who has spent time on the Chargers, Panthers and Steelers roster, and who also can play on special teams.
Wilson is familiar with inside linebackers coach Jim Leavitt, having played for him at the University of South Florida.
Et cetera – Cornerback Tramaine Brock (ankle) was on hand for the early part of practice but did not take part in the full session. He was injured July 27. Another cornerback, Chris Cook, is dealing with a minor knee injury and did not practice.
Tackle Jonathan Martin missed practice while dealing with a personal matter. With Adam Snyder (knee) also out, Ryan Seymour lined up at right tackle with the first-team offense.
Rookie cornerback Kenneth Acker, a sixth-round pick out of SMU, had two interceptions Wednesday afternoon.
Read Matt Barrows’ blogs and archives at www.sacbee.com/sf49ers.