With seven straight victories, a revitalized offense and a big win over the Packers in frigid Lambeau Field last weekend, the 49ers are being labeled by some as the hottest and most complete team in the NFC playoffs.So when the Niners play the host Carolina Panthers this Sunday, it will be the fifth-seeded visitors from California who will be the favorites over the No. 2 seed Panthers in their own stadium. Oddsmakers have made the Panthers anywhere from 1- to 3-point underdogs.Yet in their earlier meeting this season, it was the Panthers who prevailed, 10-9. And Carolina, with a playmaking quarterback in Cam Newton, a solid ground game and a swarming defense led by All-Pro linebacker Luke Kuechly, is a confident team that believes it can beat the Niners again.So what has to happen for the 49ers to win Sunday and advance to the NFC Championship Game against the winner of Saturday's Saints-Seahawks game? Here are five keys to a 49ers victory:Offensive line: In the first matchup, Carolina dominated San Francisco's offensive line, a rare occurrence in recent seasons. The Panthers led the NFL with 60 sacks this season. They not only sacked quarterback Colin Kaepernick six times –...