Eric Heitmann might miss a second consecutive NFLÂ season because of another serious injury, and teammate Joe Staley believes he knows how this one happened.
Staley, the 49ers' starting left tackle, told the *San Francisco Chronicle* that Heitmann, the team's former starting center, injured his neck last year during former coach Mike Singletary's infamous "Nutcracker" drill, which requires two players to line up across from each other and violently hit in an effort to push back an opponent.
Singletary, a Hall of Fame linebacker known for his hits and toughness, wouldn't comment on Staley's claim when asked by Comcast SportsNet Bay Area.
"I don't know what Eric's prior situation was, so I'm not going to respond to that," said Singletary, who was fired by the 49ers toward the end of last season and now is the Minnesota Vikings' linebacker coach.
According to *The Sacramento Bee*, Singletary called the drill "pretty foolproof" at the start of 2009 training camp and said it taught players about the importance of leverage. Singletary also said he didn't believe any players would be injured during the drill, but it left linebacker Patrick Willis (ankle), cornerback Tarell Brown (toe) and center David Baas (broken foot) with injuries, according to the report.
Singletary then changed to what he said was a safer version of the drill for 2010 camp, but Heitmann and linebacker Derek Walker were also injured.
According to Staley, Heitmann felt a neck tweak after one of the drills at last year's camp but continued to practice with it. Misfortune struck Heitmann the next day, when he broke his left leg, ending his 2010 season. But he felt numbness and pain in his neck until last month, when he had surgery that could cost him the 2011 season.
Heitmann's agent, Kenny Zuckerman, told CSN Bay Area on Wednesday that it normally takes about six months to recover from the surgery, which repaired a ruptured disk. That would make it late November or early December before his client might be ready to return. Heitmann's contract expires after the 2011 season.
Heitmann, 31, has started 114 games since the 49ers selected him out of Stanford in the seventh round of the 2002 NFLÂ Draft. Until last season, had missed just two starts in six seasons.
David Baas, who replaced Heitmann as the starting center last season, isn't under contract. According to the Chronicle, unsigned Tony Wragge, rookies Mike Person and Daniel Kilgore, and veteran Adam Snyder are candidates to play center.
