The 49ers offense missed more than Frank Gore on Saturday. Pass protection might have been helpful, too, in an eventual 30-7 exhibition loss to the Houston Texans.

Multiple lapses by the offensive line sparked subpar efforts from quarterbacks Alex Smith and Colin Kaepernick, who combined to complete 8 of 22 passes for 69 yards with an interception each.

"Obviously we took our lumps tonight," Smith said. "It was a rough one for all of us."

Those puny passing yards at least surpassed the 55-yard output of a 49ers rushing attack missing Gore, whom coach Jim Harbaugh kept on the sideline in order to evaluate younger backs Anthony Dixon and Kendall Hunter.

All the offensive misery overshadowed two positives: Linebacker Ahmad Brooks' 13-yard interception return for a 49ers touchdown on the game's first snap, and the 49ers sustained no significant injuries, a welcome trend this exhibition season.

Those highs -- and disturbing lows -- played out in front of a half-empty Candlestick Park, site of disturbing fan violence at last week's exhibition win over the Raiders. Only a few thousand fans remained in the stands before Saturday's fourth quarter.

While there was beefed-up security off the field, the 49ers quarterbacks could have used extra protection on it. The Texans' four-man rush proved nearly as menacing as the New Orleans Saints' blitz-heavy scheme in the 49ers' exhibition opener.

"It's not real complicated what they were doing up front, but they were getting us, they were beating us," Harbaugh said. "I'm not aware of any communication issues."

Left tackle Joe Staley got beat on a third-down sack of Smith on the 49ers' first offensive series. Smith got sacked on the next possession by Antonio Smith, who shot past left guard Mike Iupati.

"I made a mistake, and I've got to learn from it," Iupati said. "I didn't play my game."

Alex Smith got drilled on his final pass of the night -- again by Antonio Smith, who this time beat center Jonathan Goodwin. The 25-yard throw by Smith got intercepted by safety Troy Nolan 12 seconds before halftime.

Smith started the first two series, sat out the next two and returned for the 49ers' final two series of the first half. He posted a 2.8 passer rating by completing 2 of 6 passes for 17 yards.

Kaepernick finished 6 of 16 for 52 yards with a 20.8 rating. His first series ended with an interception that Nolan returned 73 yards for a touchdown and a 24-7 Texans lead. Just like that, Kaepernick had thrown his first touchdown pass as a 49er, albeit to an opponent.

"(Harbaugh) asked me if I saw the safety, if I saw what was going on. I told him, 'Yeah,' " Kaepernick said. "He said, 'All right, we'll just move on from there, we'll learn from it.' "

The 49ers are still trying to learn their right combination on what is a young offensive line. Adam Snyder started at center before briefly moving to right guard, with Goodwin taking over at center. Alex Boone also is seeing time as a backup at both tackles.

"It's not something I'm worried about," Smith said of the line's evolution. "We've got a good group up front that works as hard as anybody and is talented."

Harbaugh said he would not consider turning to Kaepernick as the starting quarterback just because his mobility may work better behind a suspect line.

With Gore on the sideline -- and awaiting the outcome of Monday's contract-extension talks -- Anthony Dixon started and had eight carries for only 15 yards. Kendall Hunter produced 40 yards on his eight carries.

Defensively, the 49ers weren't as stout as a week ago as the Texans rolled up 417 yards.

Quarterback Matt Schaub (16 of 24, 180 yards) became the first starting quarterback to engineer a scoring drive against the 49ers this exhibition season, breaking that barrier when Derrick Ward scored on a 1-yard run with 33 seconds left in the first quarter.

Schaub had two passes result in touchdowns: A 12-yarder to tight end Owen Daniels midway through the second quarter and the 13-yarder that the 49ers' Brooks returned for an instant touchdown and 7-0 lead.

"We got off to a great start with Ahmad's interception," safety Madieu Williams said. "But I thought we were not as sharp as we were the previous week on getting off the field on third down."

The Texans converted 9 of 15 third-down opportunities into first downs. In contrast, the 49ers were 2 of 10 on third-down conversions.

If that doesn't sum up the offensive disparity, this might: The combined passer rating of Smith and Kaepernick: 7.6.