The San Francisco 49ers' stellar defense is a major reason they enter the second half of the season in control of the NFC West, at times overshadowing an offense possessing an efficient quarterback and the NFL's best running game.

Alex Smith , Frank Gore and the rest of the 49ers' offense look to take advantage of a St. Louis Rams team that hasn't forced a single turnover during a three-game losing streak when the division rivals meet Sunday in San Francisco.

Defense has been a staple of coach Jim Harbaugh's squad that is allowing an NFL-low 12.9 points per game while giving up an NFC-best average of 271.4 total yards.

San Francisco (6-2) has won four of five, allowing a total of 12 points without a single touchdown in the victories after beating Arizona 24-3 on Oct. 29 before its bye week.

The offense hasn't been bad, either. Smith ranks fourth in the league with a 102.1 passer rating after finishing 18 for 19 for 232 yards and three touchdowns - two to Michael Crabtree and another to Randy Moss - versus the Cardinals.

Gore had only 55 yards on 16 carries, but he's a big reason the 49ers lead the NFL with 168.6 yards per game on the ground. Three victories during San Francisco's hot stretch have come by at least 21 points.

"When you see other teams, other players, you see one or two guys having big stats," Gore said. "In this offense, it's different. There's so much talent around here."

Though Harbaugh surely is pleased with his team's effort on both sides of the ball, he knows there's plenty of work to be done if the 49ers hope to play in their first Super Bowl since the 1994 season.

"A simple approach to how we understand success is to get better today than we were yesterday. Be better tomorrow than we were today," Harbaugh said. "Feel like improvement will lead to wins. And wins will lead to championships. It's an improvement-equals-success theory."

San Francisco has committed only nine turnovers, and the chances of that number increasing against struggling St. Louis seem slim.

The Rams (3-5) took an early 7-0 lead before allowing 45 unanswered points in losing to New England on Oct. 28 in London before their bye week.

It also marked their third consecutive game without a takeaway. They've forced only two fumbles all year, much to the dismay of coach Jeff Fisher.

"It's highly unusual that in eight games and all the touches that are involved in eight games, our opponent has fumbled two balls and we've recovered one," Fisher said. "We need to place a great deal of emphasis on that and getting the ball back."

The Rams, who only have nine total takeaways, haven't gone four straight without forcing a turnover since at least 1950.

"We have got to find a way to come up with some big plays," linebacker James Laurinaitis said. "Defensively, we have got to force some turnovers. We are in a drought with that right now, so how do we force some turnovers? How do we make some plays? How do we score on defense? How do we impact the game more?"

On offense, Sam Bradford has been solid during the team's skid, completing 67.0 percent of his passes, including a 50-yard touchdown to Chris Givens against the Patriots.

Bradford missed both meetings with the 49ers last season while recovering from a high left ankle sprain, but he has a 73.4 completion percentage and 100.3 rating with two touchdowns in two career starts versus San Francisco.

"He's always been a pretty top-notch guy (and has) all the things you look for from a top notch quarterback in this league," Harbaugh said. "He's got a calm demeanor in the pocket. Excellent technique, footwork, arm strength, real good location."

Bradford could benefit from the return of favorite target Danny Amendola , who still leads St. Louis with 32 catches and 395 yards despite missing the last three games with a collarbone injury.

"It's feeling good right now, I have full range of motion and strength and everything," Amendola said.

Smith threw for 213 yards and Crabtree caught two touchdowns - one on a fake field goal - in the 49ers' 34-27 victory in the most recent meeting Jan. 1, marking their seventh win in the last eight matchups.

St. Louis hasn't won in San Francisco since 2007, dropping four straight and six of the last seven there.

Rams, 49ers play to 24-24 tie

SAN FRANCISCO (AP) -- Two typically reliable kickers missed. Penalties doomed both sides. And a furious, thrilling finish to regulation ended with a dramatic dud in overtime: a tie.

And nobody particularly likes a tie. Especially not the NFC West-leading 49ers, with a chance to separate themselves against a division rival. Or the Rams, eager to snap a three-game losing streak.

San Francisco and St. Louis played the NFL's first tie game in four years as both teams missed overtime field goals in Sunday's 24-24 outcome.

"I have to say, I've been doing this a while. I don't think I've ever been in a game like this," Rams coach Jeff Fisher said. "As I told our guys, we had a number of chances to put the game away. And, unfortunately, we didn't."

Greg Zuerlein kicked a 53-yarder, but the Rams were penalized 5 yards for delay of game - which holder Johnny Hekker said was his fault. Zuerlein tried again from 58 as Fisher played for the win, and missed wide right with 2:42 left in OT.

San Francisco's David Akers missed wide left on a 41-yard attempt that could have sealed it for the 49ers (6-2-1), who lost quarterback Alex Smith to a first-half concussion.

And just when it seemed the 49ers - and Akers' typically reliable left leg - would have one more chance to win it, San Francisco linebacker Patrick Willis was flagged for holding Lance Kendricks on third down. That extended St. Louis' last drive, a costly mistake in a long list of them on an uncharacteristically sloppy day by coach Jim Harbaugh's team.

"I don't know what to make of this," Willis said. "We have one of the best kickers in the game, and it came down to him at the end and he misses it. That tells you right there something wasn't right."

Akers booted a tying 33-yarder with 3 seconds left in regulation after Sam Bradford threw a 2-yard touchdown pass to Austin Pettis with 1:09 remaining.

On the first play of OT, Bradford completed an 80-yard pass to Danny Amendola that took St. Louis (3-5-1) to the 2, but the play was called back for an illegal formation. Some 49ers fans got up to leave, then returned to their seats.

The last tie was between Philadelphia and Cincinnati, 13-13 in 2008. San Francisco played its first tie since 1986.

Frank Gore ran for a 20-yard touchdown with 8:23 to go in regulation just 17 seconds after backup quarterback Colin Kaepernick scurried 7 yards for a score. Kaepernick finished 11 for 17 for 117 yards and also had eight carries for 66 yards, calmly leading the Niners after it took several series to find his groove.

"It just feels like it's unfinished business," San Francisco cornerback Tarell Brown said.

Gore ran for 97 yards, while Michael Crabtree made five catches for 70 yards and a 14-yard touchdown from Smith before he left the game.

Amendola returned for the Rams following a three-game absence with a shoulder injury to make 11 catches for 102 yards. Bradford went 26 for 39 for 275 yards and two touchdowns.

Smith took a hard hit on the back of the neck from linebacker Jo-Lonn Dunbar after a scramble with 1:10 left in the first quarter. But the No. 1 overall pick in the 2005 draft stayed in and completed his next five passes, including Crabtree's TD.

After the hit, Smith was sacked three plays later and also clobbered again on a fourth-and-1 keeper. Doctors indicated to Harbaugh that might have been the play that caused injury.

Harbaugh said Smith would be evaluated this week per NFL concussion protocol. He wasn't available to speak to reporters. Smith, who has started 28 straight games, wound up 7 for 8 for 72 yards.

The 49ers didn't face Bradford in either meeting last season as the Rams quarterback missed six games with a high left ankle sprain. He had all kinds of extra opportunities this time.

"It's a weird feeling. I've never been a part of a game like that before," Bradford said. "I think the mood in this locker room is disappointment."

Late in the third period, the Rams benefited from Dashon Goldson 's 15-yard unsportsmanlike conduct penalty for taking off his helmet. Then, defensive tackle Ray McDonald was flagged for a helmet-to-helmet hit on Bradford when he came in under the quarterback's chin, extending another Rams drive. Zuerlein kicked a 27-yard field goal.

The penalties and miscues were certainly uncharacteristic of San Francisco's defense.

Crabtree's touchdown midway through the second quarter gave him a TD reception in five straight games against the Rams. It was his third touchdown in two games, and all of his team-leading four TD catches have come in the last five games.

Kaepernick took over as Smith went to the bench to be examined by medical personnel and soon left for the locker room.

One wild play late in the first half summed up this wacky day. Punter Hekker completed a 21-yard pass to safety Rodney McLeod from the end zone after Chris Culliver didn't cover McLeod. Hekker did it again in the fourth quarter and had a notable 118.8 passer rating on the day.

On the Rams' 14-play, 18-yard drive over the final minutes of regulation, Hekker faked an end-around and threw a 19-yard completion to Kendricks on fourth-and-8 from the Rams 33.

But the Rams' defense couldn't get a stop, allowing Kaepernick to get his team back into field-goal range for Akers to tie it.

The Rams played without a pair of starters held out for an unspecified team rules violation, cornerback Janoris Jenkins and wide receiver Chris Givens - and Fisher said afterward he isn't sure if they will play next week at home against the New York Jets .

The 49ers will regroup to face the Bears in prime time.

"It feels weird," safety Donte Whitner said. "We're about wins around here."

Notes: Rams LT Wayne Hunter played after missing two games with a back injury. ... Fans spelled out "THANK YOU VETERANS" in the stands with shiny red, white and blue cards after the first quarter. A special military coin also was used for the pregame toss on Veteran's Day.

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