A golf ball includes a thermoplastic inner core layer having a geometric center hardness less than a surface hardness to define a “positive hardness gradient.” An outer core layer is disposed about the inner core, the outer core being formed from a thermoset rubber composition and having a surface hardness less than a hardness at a point about 0.5 to 2 mm from an interface between the inner core and the outer core layer to define a shallow “negative hardness gradient.” An inner cover layer is formed over the outer core layer and an outer cover layer is formed over the inner cover layer. The “positive hardness gradient” of the inner core is up to about 10 Shore C and the shallow “negative hardness gradient” of the outer core layer is less than about 10 Shore C.
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