Stuart, who has an injured rib, will miss a minimum of one week.
The 25-year-old Leino is second on the Griffins in scoring with 37 points in 44 games. He had six points in eight preseason games for Detroit, which signed him as a free agent on May 10.
Downey has six points and 71 penalty minutes in 44 games for Grand Rapids this season. The 34-year-old had three points and a team-high 116 penalty minutes in 56 games for the Red Wings in 2007-08.
Stuart has eight points and 18 penalty minutes in 45 games with Detroit this season. He signed a four-year contract in July.