SANTA CLARA, Calif. -- The San Francisco 49ers' offense challenges opponents to stop them on the ground.The Carolina Panthers' defense dares opposing offenses to run on them.The 49ers have won five straight game and the Panthers have won four straight games. This game of the two streaking teams may be decided on the ground.The 49ers have the NFL's fourth-ranked run offense and, according to ESPN Stats & Information, it leads the NFL by calling running plays on 50.