It doesn't get mentioned a lot, but the Eighth Circuit upheld Nebraska's gay marriage ban in 2006. I think that court's an even bigger possibility for a circuit split (if that case didn't already establish a split).
I can't see where any pre-
Windsor circuit decisions on the issue could be used to justify the existence of a circuit split. Indeed, it's fairly clear that the Eighth Circuit ruling then was in line with the precedents available, plus the only reason the Eighth even took the case was because Judge Bataillon of the Nebraska District is an overreaching activist idiot. Two of his three arguments for overturning it were of such bogosity, its hard to believe someone who wasn't suffering from advanced dementia would think they had any soundness so I hope Bataillon included them solely in hopes that when appealed, the circuit court would be satisfied to throw out his two totally bogus justifications while leaving his third intact.