SANTA CLARA -- Weston Richburg is one veteran who is not complaining about a long training camp and a four-game preseason schedule.

That’s because Richburg, the 49ers’ highest-priced free-agent pickup, believes he needs just about every opportunity to learn the requirements of his center position before the start of the regular season on Sunday, Sept. 9, against the Minnesota Vikings.

“I came from a different offense, and we’re just learning, trying to figure out, how to do my job best,” Richburg said. “And that just takes reps. That’s the good thing about being able to go to practice and getting those reps.”

The 49ers’ first-team offense struggled in the run game in the first two preseason games. As a team, the 49ers have averaged just 3.4 yards per rushing attempt. In the opener, starting running back Jerick McKinnon was thrown for minus-4 yards on three rushing attempts.

McKinnon and Matt Breida, the 49ers’ top two backs, will be out until the start of the regular season because of calf and shoulder injuries, respectively. The 49ers last week signed veteran running back Alfred Morris.

The problems, Richburg said, are to be expected, as the offensive line works to understand the intricacies of Kyle Shanahan's running game.

“It’s the tiny details,” said Richburg, who signed a five-year, $47.5 million contract as a free agent. “The run game is all about angles and figuring out how to get a certain point, taking into mind where the D-line is and where the linebackers are going to go.

“So it's just figuring out those tiny details of where we need to be and when we need to be there to give our skill guys the best chance to go make a play.”

Lynch wishes Harold well

The 49ers officially announced the trade of outside linebacker Eli Harold to the Detroit Lions. He must pass a physical for the trade to be completed.

Said general manager John Lynch in a statement: "Our entire organization would like to thank Eli for his hard work and contributions to our team and the Bay Area community over the last three years. He always represented the 49ers with class and has been a tremendous teammate. We wish Eli and his wife, Kelsey, nothing but the best in the years to come.”

Sherman calls helmet rule ‘idiotic’

The NFL’s new helmet rule does not appear to be going away. But veteran cornerback Richard Sherman said it is useless for him, or other players, to spend too much time figuring out what is and is not acceptable.

He was asked how much time he has spent trying to figure out what warrants a 15-yard penalty for initiating contact with the helmet.

“Zero,” he answered. “Zero, because it’s an idiotic rule, so there’s no need to even go down that road. There’s no way you can tackle the way they’re asking people to tackle and play football. I could probably tackle like that if I were standing still and got on my knees and nobody was moving and I was tackling bags or something.”

Troy Vincent, the NFL’s executive vice president of football operations, stated Wednesday that no changes would be made to the helmet rule. But the NFL Competition Committee determined that “inadvertent or incidental contact” with the helmet or facemask is not a penalty.

One of Sherman’s gripes about the rule is that it appears as if officials are calling the penalty only on defensive players. He cited an instance in the Minnesota-Jacksonville preseason game in which Vikings running back C.J. Ham lowered his helmet and plowed over Jaguars cornerback A.J. Bouye. But the penalty was called on Bouye, not the running back who initiated contact.

This ‘N’ That

Richburg had a forgettable sequence in the 49ers’ game Saturday at Houston. He was called for holding, then he was immediately slapped with an unsportsmanlike conduct penalty for a total of 25 yards in infractions. But the NFL sent a memo to the 49ers critiquing the performance of the officials, and Richburg said the league admitted the holding penalty was a bad call. However, the unsportsmanlike penalty still applied. “I just told him I didn’t think it was a hold,” Richburg said of his interaction with an official that warranted the second penalty. “We’ll leave it at that.” . . . The 49ers have generated little pass rush in the first two preseason games. It appears to be tempting for the club to line up DeForest Buckner more as an outside rusher. “He’s our best player,” 49ers defensive coordinator Robert Saleh said. “So the challenge for us as coaches is to find a way to get him one-on-ones as many ways as possible.” . . . Rookie defensive back D.J. Reed is showing the versatility to be a valuable piece of the team’s secondary as a backup safety and backup nickel back. “His arrow is up,” Saleh said. “We love him, and the thing about it is we love his mindset. That young man just is, talk about all gas, he’s awesome. He’s doing a good job, he really is. For him to solidify that spot (backup free safety), there’s still two weeks left. There’s nothing set in stone yet.”