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Brandon Jacobs hasnt let go of his disdain for former San Francisco 49ers head coach Jim Harbaugh. The former NFL running back recently said on CBS Sports Radio that the current Michigan head coach didnt know what he was doing.

Jacobs wasnt done taking aim at his former coach, vowing on Twitter to expose him and eventually get him fired. So why is Jacobs so upset at Harbaugh that he wants to ruin his career?

Jacobs joined the 49ers in 2012, the second year of Harbaughs four-year run as head coach in San Francisco. The then-30-year-old running back had his 49ers debut delayed initially by a knee injury.

Once he was healthy, Jacobs played sparingly and vented about his lack of activity. As the weeks became months, Jacobs frustrations grew. He didnt play until Week 12 against the Saints and finished the season appearing in just two games and totaling 7 yards on five carries.

After venting on social media sites about his dissatisfaction with the team and Harbaugh, the 49ers suspended him for the final three games of the season.

All of this has led to Jacobs ongoing attack of Harbaugh, who opted to take the high road on Twitter.

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