For someone who claims to be a tennis fan, you do not know a whole lot! Stan just beat two of the mentally toughest guys of all time in Australia to win his first major having stuffed Murray at the US Open last summer and for good measure Stan also put the smack down on Murray at the US Open in 2010.
I'll correct that for ya bud.... Stan's 'big' wins came against injured opponents. A 100% fit Nadal or Murray would beat him ...and in straight sets most likely. Fed only beat Murray at the Oz because Andy wasnt 100% fit at the time.
In a Davis cup scenario Id say Andy would win his singles matches and therefore GB would require 1 more point from the other 3 matches.... entirely feasible GB could win the tie.