Brandon Jacobs' first season with the San Francisco 49ers will likely be his last as the the veteran running back took to social media to express his frustration with his playing time this season. "I am on this team rotting away so why would I wanna put any pics up of anything that say niners." Jacobs wrote on Instagram, according to Matt Maiocco of CSNBayArea.com. "This is by far the worst year I ever had, I'll tell you like I told plenty others." Released by the New York Giants for salary cap purposes in March, Jacobs lingered on the free-agent market until agreeing to terms with the 49ers on March 28. The one-year, $1.6 million contract, with $400,000 in incentives, was signed on April 7, with Jacobs receiving a $150,000 signing bonus. Jacobs received a $300,000 bonus for being on the roster in Week 1 and is earning a $950,000 base salary. Jacobs also receives an additional $12,500 for each game he's on the team's 46-man game day roster, but thus far, he has earned only three of those "per game active" roster bonuses. [More NFL: Best teams for QB Tim Tebow, who still lacks basic skills ] After missing a month of the season with a knee injury, Jacobs finally dressed, but did not...