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)
Georges St. Pierre*Sarra McMann*Pat Curran*Patricio Freire*Uriah Hall
NP FFL Team Toxic Challenge
Fabricio Werdum*Gilbert Melendez*Rick Hawn*John Dodson*Urijah Faber