The 49ers’ offense is anchored by the running game, and with Frank Gore and Kendall Hunter they employ two highly talent rushers who complement each other. The problem is that Gore is so injury prone that merely typing his name led to a pinky finger sprain, and now I’m struggling to access the upper reaches of my keyboard (#firstworldproblems).

Gore ranked sixth in rushing with 1,211 yards and eight touchdowns in 2011, and he did it while playing in a full 16-game season for just the second time in his seven-year career. But he was still slowed by an ankle injury, essentially missing a Week 10 win over the Giants (he had six carries for zero yards). Between 2008 and 2010 Gore missed nine games, and he’s 28, meaning he’s quickly approaching the running game dark hole age.

Hunter was drafted in the fourth round last year to ease Gore of his backfield burden, and in limited time the rookie had 473 rushing yards on 112 carries. But when the running game is the cornerstone of your offense (which may change slightly in San Francisco with Randy Moss and Mario Manningham now aboard, but I digress), insurance is paramount.

Enter Brandon Jacobs, the now former Giant who agreed to a one-year deal with the 49ers, according to ESPN’s Adam Schefter.

Jacobs will turn 30 in July, so he’s about to be sucked in by that block hole too. But that’s fine, because he’ll be both a depth option for Jim Harbaugh, and a bruiser playing a very specific role in the Bay Area. Whereas in New York Jacobs often nearly split carries with Ahmad Bradshaw and averaged 10.9 carries per game this past season, he’ll primarily be utilized by the 49ers as a short-yardage back.

Jacobs’ large body and his ability to hurt people at the goal-line also addresses a glaring offensive weakness. Although they improved in the final games of the season, at one point in early December the 49ers had scored only three touchdowns on 20 red-zone possessions.

For the Giants, this is a Jacobs-sized blow. Their fourth-round pick from 2005 will continue to slow with age and be hampered by injuries, but Bradshaw has struggled to stay healthy too, and he’s only 26. Similar to Gore, Bradshaw has played just one full season, and he missed four games with an ankle injury that landed him under a surgeon’s highly-skilled knife a few weeks ago.

When he felt like playing, Jacobs was perfect in the Giants’ offense, and had the ideal blend of power and athleticism for a runner of his size. That fit alongside Bradshaw will be difficult to find again, and Jerry Reese may be forced to change his draft strategy and tap into the RB market a little earlier.