SANTA CLARA -- Linebacker Patrick Willis sustained a fracture in his right hand during the 49ers' practice Wednesday but will be ready to play in the Sept. 8 regular-season opener, according to an ESPN report.
Willis has broken the same hand twice earlier in his career, and he played with a cast in both his 2007 rookie season and late in the 2010 season. He also wore a cast on his right hand most of his penultimate college season at Mississippi,
Coach Jim Harbaugh will address the media after Thursday's practice, which is slated from noon to about 3 p.m. Harbaugh typically refrains from commenting on players' injuries.
Willis' status for the four exhibition games is uncertain but it's doubtful the 49ers would risk playing the All-Pro linebacker in those contests, starting with an Aug. 8 game against the Denver Broncos at Candlestick Park.
Michael Wilhoite took Willis' spot on the first-string defense in Wednesday's team drills and likely will continue to line up there next to NaVorro Bowman, who is also battling an injury, believed to be a groin strain.
"Michael's coming along great," Willis said earlier this week. "Every time he gets an opportunity to be out there, he performs the way he's supposed to, and he gets more comfortable the more reps he gets."
The 6-foot, 240-pound Wilhoite appeared in five games last season as a special-teams call-up from the practice quad, where he had been since late in the 2011 season. Last season, Wilhoite won the team's Thomas Herrion Award, given annually to a rookie or first-year player who takes advantages of his opportunities and "made their dream turn into reality."
Another inside linebacker to keep an eye on in the exhibitions is rookie Nick Moody. The sixth-round pick from Florida State has impressed with speed and aggressiveness a week into training camp.
"You've always got to remember he was a defensive safety in college until his last year there," defensive coordinator Vic Fangio said of Moody. "So, he's relatively new as a linebacker and that shows up at times. And, then other times his talent shows up and makes you think he can be an NFL linebacker."
The 49ers signed San Jose State product Travis Johnson on Tuesday to replace linebacker Darius Fleming, who re-tore an anterior cruciate ligament Sunday.