The Pistons have tendered a qualifying offer to Jalen Duren, officially making him a restricted free agent, says Keith Smith of Spotrac (Twitter link). The move is mostly procedural since keeping Duren is an offseason priority in Detroit, and the QO – which is worth $9,615,393 – gives the team the option to match any offers he receives in free agency. As Smith notes, the more important question is how much the Pistons are willing to spend to re-…