Those teams converted 16 of 27 chances in recent victories over St. Louis.
Early downs could present the biggest challenge for the Rams against San Francisco in Week 10. The 49ers like to line up with multiple backs and/or tight ends to stress opponents' base defenses. That will be a key matchup Sunday at Candlestick Park.
As the chart shows, the 49ers are averaging 6.3 yards per carry and 9.2 yards per pass attempt against 4-3 defensive personnel on early downs. Those figures both rank third in the NFL.
The Rams allow 4.0 yards per rush and 7.9 per pass attempt from their 4-3 defense in those situations. League averages are 4.4 and 7.8, respectively, for the 20 teams regularly running 4-3 alignments as their base defenses. Those are respectable figures overall, but a look inside the numbers reveals some inconsistencies.
The Seattle Seahawks and Washington Redskins fared better. Seattle carried 23 times for 141 yards while also averaging 8.2 yards per pass attempt in these situations. Washington used play-action from regular personnel to strike for a 68-yard touchdown when the Rams' base defense stacked eight in the box on first-and-10.
"The SAM backers, whether it was [Rocky] McIntosh or [Mario] Haggan, have just been a wash," Venturi said. "They've been totally mediocre, but they don't play very much. Very few people play 21 or base personnel [frequently] any more. That is going to change this week in San Francisco. Those guys are going to have to earn their money."
The 49ers have executed 65.6 percent of their first- and second-down rushes from two-back sets. They have averaged 5.5 yards per carry when doing so.