Bush, 30, signed a one-year, $2.5 million contract with the 49ers back in March that included $1.1 million guaranteed. He’ll be an unrestricted free agent again next year.
Entering today’s game, Bush had appeared in four games and ran for 28 yards on eight carries (3.5 YPC) to go along with four receptions for 19 yards receiving and no touchdowns.
Thomas, 30, had two years remaining on his three-year, $6.9 million contract when the Saints elected to release him in a move that freed up $1.735 million in available cap space.
He was, arguably, the best running back still available, and had worked out for the Chiefs in Texans since the start of the season.
The 49ers brought him in for a tryout a few weeks ago, so he was clearly on their radar.
In 2014, Thomas ran for 222 yards on 45 carries (4.9 YPC) to go along with 45 receptions for 378 yards receiving and three touchdowns. Pro Football Focus has him rated as the No. 9 running back in the league out of 57 qualifying players.