The terms of the deal were not disclosed, but NFL's Ian Rapoport reports it is a two-year contract worth $3.9 million total. He also reports that the deal is incentive-based, and the contract could go up to $4 million per season.
The Indianapolis Colts waived Richardson earlier this month after a season in which his production declined and the team reportedly was frustrated with Richardson for several reasons, including issues with his weight.
Richardson missed the AFC Championship Game after Indianapolis suspended him for not telling the team that he would miss a walk-through. Richardson was also set to be suspended for one game next season.
Richardson reportedly filed a grievance against the Colts over the suspension.
The 23-year-old began last season as the Colts' starter but averaged just 3.3 yards per carry over 15 games and saw his role diminish later in the regular season, with Boom Herron seeing an increased workload.
Richardson was selected No. 3 overall in the 2012 draft out of Alabama.