Sims' best season came in 2015 when he had 529 yards rushing and 51 receptions for 561 yards receiving. He also had four total touchdowns.
The 27-year-old Sims has struggled in the last two seasons and became a free agent in March after his rookie contract expired. He ran just 95 yards in 2017 to increase his career totals to 958 yards rushing and two rushing scores in 47 games since being selected by the Buccaneers in the third round of the 2014 NFL Draft.
Martin rushed for a career-low 406 rushing yards last season and has been limited to 827 over the last two campaigns after erupting for 1,402 in 2015.
The 29-year-old Martin burst on the scene after Tampa Bay selected him with the 31st overall pick of the 2012 NFL Draft. He rushed for 1,454 yards, amassed 12 total touchdowns and added 49 receptions for 472 receiving yards, with all four totals serving as career highs.