#Tigers will not go after Cliff Lee, or a top-tier FA pitcher of that ilk. That doesn't mean they'll only pursue 5th starters, though.
As of right now, the top four of Detroit's rotation looks like this: Justin Verlander, Max Scherzer, Rick Porcello and Phil Coke. Detroit could obviously fill that fifth spot with someone who is the caliber of a fifth starter, but as Beck points out, there's no guarantee that will happen. Detroit could easily go after a third or fourth caliber pitcher, which would just end up moving Coke down to the fifth spot.
We do know that Detroit won't be shelling out big bucks for another top pitcher, though.