Brown, 32, has found limited interest as a free agent this year, but he did have a tryout for the Patriots back in May.
Brown signed with the San Diego Chargers for the last two seasons, and has reinvented himself as a third-down back, excelling at blocking and catching the ball out of the backfield.
He appeared in 16 games last year and ran for 157 yards and added another 60 yards receiving while scoring one touchdown.
Leonard, 30, is clearly among the best available running backs. He spent the 2013 season with the Bengals and ran for 182 yards on 47 carries (3.9 YPC) and caught 29 passes for 179 yards receiving. Pro Football Focus has him rated as the No. 20 running back last season out of 55 qualifying players.