There's a good reason quarterbacks are often taken at the top of the first round, even if they aren't the best player available (Ryan Tannehill in 2012, Christian Ponder and Jake Locker in 2011, etc.).
NFL teams can't win games without a legitimate franchise quarterback, and Cassel doesn't cut the mustard. He's not the only starting quarterback in need of being replaced, either.
These teams all need to find upgrades for their current quarterbacks.