Weekley might be the guy who helps get the US on the right track with regards to team play. He is a fun, happy, fiercely competitive player. A guy that could go out there and be the American version of Sergio Garcia in team play.
Boo Weekley has a swing that a lot of people should watch. He is proof that you don't have to be crazy flexible in order to be good. He has some flexibility, but not like that of Tiger, Vijay, or Garcia.
He has a more controlled motion between his lower body and upper body. They turn together during both his backswing and downswing. This loses a bit of power, but can make him very consistentThe more flexible players will create a separation between the lower body drive on the downswing, and the upper body following.
If you struggle with flexibility, or have a condition that affects your back try turning your shoulders and hips together. It will take pressure off your back and help you be a more consistent ball striker.