The 49ers' passing attack can score quickly, as shown by the 27-yard touchdown from Colin Kaepernick to Anquan Boldin at the start of the second quarter.
But is also makes a lot of mistakes.
Kaepernick has been sacked six times, lost a fumble and nearly threw two interceptions in the opening half, which is the main reason the Rams tied the game 10-10 at halftime. Their 21-yard touchdown followed Kaepernick's fumble. It came on a crossing pattern to Kenny Britt, who ran past rookie linebacker Chris Borland, who did not start trailing the Rams receiver until he was wide open.
The 49ers' defense, however, mostly was solid.
Safety Antoine Bethea, who has been perhaps the team's MVP so far this season, mirrored Rams quarterback Austin Davis as he rolled out of the pocket early in the second quarter and then leaped to intercept Davis' pass attempt to Tavon Austin at the St. Louis 35 yard line.
Three plays after that, the 49ers used a bit of misdirection.
They called a play that had Bruce Ellington and Frank Gore in the backfield and tight ends Vernon Davis and Derek Carrier on the right side of the offensive line. The play went in that direction and the Rams appeared to have the primary receivers covered. But Kaepernick kept his head up and saw Anquan Boldin, who had lined up on the other side of the formation, uncovered and delivered a pass that ended up in a relatively easy 27-yard touchdown.
Davis, who was hot in the opening half of the teams' Week 6 matchup, has cooled considerably since.
On the drive after Bethea's interception, the quarterback badly underthrew a wide-open receiver deep down field. The pass was intercepted by Perrish Cox, his team-leading fourth of the season.
Since the second half of their earlier matchup, Davis is 17-43 for 173 yards with three interceptions and a touchdown.
Kaepernick is 11-16 for 126 yards at halftime. However, the six sacks he's taken in the first half equals the number of sacks the Rams had entering the game.
Read Matt Barrows’ blogs and archives at www.sacbee.com/sf49ers.