Pressure point: 49ers

Examining who faces the most challenging season for the San Francisco 49ers and why.

Frank Gore ranked sixth among NFL rushers with 1,211 yards last season, at one point rushing for at least 100 yards in five consecutive games. He earned Pro Bowl honors for his work in the regular season before adding 29 carries for 163 yards (5.6 per attempt) over two playoff games. Gore, with 7,625 yards for his career, passed Hall of Famer Joe Perry for the most in franchise history. He's been the 49ers' best and most consistent offensive player for years.

The challenge will be to remain productive and fend off challengers in an increasingly competitive backfield.

Gore's 29th birthday was Tuesday. Running backs generally slow considerably by that age. Injuries have slowed Gore at various points in recent seasons, including when he missed the final five games of the 2010 season. The good news for Gore is that his average for yards per attempt has remained strong, never dipping below 4.2 during any of his seven seasons. He's an exceedingly tough player. And although Gore is plenty physical, he runs low to the ground, making it tougher for opponents to deliver the most damaging blows.

It's possible Gore will defy the odds for older backs, putting together another robust season. He'll continue to benefit from playing within one of the NFL's best running schemes. The 49ers have bought insurance. They used a 2011 fourth-round pick for Kendall Hunter and a 2012 second-rounder for LaMichael James. They signed Brandon Jacobs in free agency. Gore remains the clear favorite to start and lead the team in rushing, but an already difficult job will become even more challenging at this stage of his career.