One reliable preview. One key factor to decide the game. It's that simple.Air Ground matchup of Week 2 (Sunday, 8:30 p.m. ET, NBC) -- The welcome the for a primetime showdown that will also serve as the first official NFL game at the new Levi's Stadium. The home team features quarterback , who through one week of play is second in the NFL with a 125.5 pa ser rating. Teaming up with Kaepernick in the backfield is 31-year-old , the NFL's fourth-oldest active running back but also one of its most effective -- the are 18-0 when Gore totes the rock at least 24 times in a game. The ' porous defense -- it allowed 5.85 yards per rush in -- could be very inviting for the to push the ground game Marquese Chriss Jersey even more.The ' offense was supposed to light up scoreboards this season. It didn't exactly do that in a Week 1 lo s to the , but this unit has potential for greatne s. Quarterback has at his disposal in and . Running back is a dangerous weapon out of the backfield (he had 17 carries for 82 yards and 8 receptions for 87 yards in Week 1).One week changes everything -- Both the and were expected to compete for division titles and playoff spots this season. While the lived up to the hype by , the were on the wrong end of , who were 23-20 victors. The have an opportunity to rectify that disappointment with a victory over San Francisco and thus return to their perceived preseason quality.Great Moments in Air Ground History 61, 20 (Week 13 of 1965 season) -- On an unseasonably warm mid-December day in a game played on the muddy Wrigley Field turf, consummated in league history. Sayers scored six touchdowns (4 rushing, 1 receiving and 1 on a punt return) as the dropped a 60-burger on the visiting , . The ' journeyman quarterback, , had one of his finest days, throwing for 347 yards and three touchdowns. Follow Jim Reineking on Twitter . Austin Rivers Jersey