"The San Francisco 49ers suffered another injury to the defensive backfield.
"Antoine Bethea went down early in the second quarter of the Niners' 34-0 loss to the Denver Broncos on Sunday. The safety was blocked by receiver Cody Latimer when he went down with an apparent head injury. Bethea was then seen being escorted by medical staff to the locker room, per NFL Media's Steve Wyche.
"It was later announced that Bethea suffered a concussion and did not return for the remainder of the game.
"San Francisco signed Bethea to a four-year, $21 million contract in the offseason after eight seasons in Indianapolis. The safety has started every regular-season game in the past six seasons. Bethea was added to replace Donte Whitner, who signed a contract with the Cleveland Browns.
"He will have to go through concussion protocol to be cleared for practices and games.
"The 49ers' defensive backfield was picked apart by Peyton Manning early in the game. On a couple occasions the Niners' back-seven appeared to experience some confusion.
"On the play immediately following Bethea's exit, Manning went after replacement Craigh Dahl for a 17-yard touchdown to tight end Julius Thomas.
"The Broncos' defense didn't escape unscathed, however. Rookie linebacker Lamin Barrow went down later int the game Sunday with a 'lower leg injury' and was ruled out."
"Safety Antoine Bethea joined the 49ers' growing list of wounded starters when a second-quarter concussion spelled his exit from Sunday's 34-0 exhibition loss to the Denver Broncos.
"Bethea posted on Twitter: 'I'm doing well and I appreciate all of the concern.'
"He was injured on an apparent blow to the face by wide receiver Cody Latimer on a down-field block. Other players instantly summoned 49ers trainers to tend to Bethea, who walked off the field and later retreated to the locker room.
"I think he's OK. He'll be in our prayers,' said rookie Jimme Ward, who eventually moved to safety from his nickel back role.
"Bethea started every game the past six seasons for the Indianapolis Colts. He was among six regular starters who suited up on defense, the others being outside linebackers Aldon Smith and Ahmad Brooks, cornerback Chris Culliver, safey Eric Reid and linebacker Michael Wilhoite."
"In another development, 49ers head coach Jim Harbaugh was none too pleased with San Francisco's execution against Denver, per ESPN's Bill Williamson:
"What was the San Francisco 49ers' locker room like after a 34-0 loss to the Denver Broncos to usher in Levi's Stadium? Not concerned.
"'Nothing to worry about,' tight end Vernon Davis said, cautioning the preseason is simply for 'working out kinks and giving young players a chance to play.'
"Added running back Frank Gore: 'It's just camp.'
"Gore said he is not worried because the 49ers look fine in practice.
"While the players are taking a positive approach, 49ers coach Jim Harbaugh was more pointed. He said his team overall is lacking precision at this point.
"'That's football. It punishes mistakes,' Harbaugh said. 'It rewards execution and precision.'
"Harbaugh said he wants to see significant improvement next Sunday when the 49ers play host to San Diego. That's the game the starters usually play into the second half.
"'It's off right now,' Harbaugh said. 'Definitely off, in correctable ways. That's what I see. Feel like we can get it corrected."