Shields isn't likely to submit GSP. Shields is a good grappler but lets be realistic he hasn't submitted anyone who was really that good. His biggest wins have been based on lay and pray for the most part.
"If you get hit and it hurts hit him back you not knocked out yet."-Joe Doerksen
The Toxic Terrors (FFL)
Demetrious Johnson*Eduardo Dantas*Rafael Silva*Zach Makovsky*Michael Page