SANTA CLARA, Calif. – Here is a look at what the San Francisco 49ers must do and can't do Monday against visiting Atlanta:Must happen: The 49ers have to contain quarterback Matt Ryan. The player whom the 49ers stopped in the NFC Championship Game last season has been struggling. But he is still dangerous. He is still capable. The 49ers' defense has been fabulous, especially in the second half of the season. It should be able to keep Ryan from taking over.