Lets break it down:
Petro and Shatts are manning the top PP in STL.
Whitney a bandaide boy
Foster is full of questions marks (IMO)
Seabrook gets next to no PP, and is only valuable if block shots and hits are involved.
In summary don't drop Shatts! Players will have hot and cold spells, ride it out and you won't be disappointed.
Good luck with your choice,
Cheers