The San Francisco 49ers showed why they're the NFC West champions in the second quarter of Sunday's game against the St. Louis Rams. After trailing 7-0 early, the 49ers have scored 20 unanswered points to take a 20-7 lead going into halftime as they try to clinch the No. 2 seed in the NFC.

Quarterback play is a key part of why the 49ers are leading. Alex Smith has been fantastic for San Francisco, completing 14 of 20 passes for 158 yards and a touchdown while running in another. The Rams, meanwhile, have struggled in the passing game. Kellen Clemens has completed just 4 of 10 passes for 66 yards, he's been sacked twice, and Jerious Norwood threw an interception on a trick play.

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