  We report our finding of a two scale cut off structure in the infrared
nonperturbative dynamics of Pade couplant QCD, in the flavor states $N_{f} \le
8$. We argue that these two NPQCD momentum scales $Q_{c}(Y_{1})$ and
$Q_{c}(Y_{2})$ can be identified as the scales of onset of chiral symmetry
breaking and quark confinement in QCD, and as the cut off boundaries of a
strongly interacting infrared quark gluon phase of Quantum Chromodynamics,
intermediate between the hadronic phase of QCD and the weakly coupled
perturbative QCD regime. We investigated the pattern of variation with flavor
number $N_{f} \le 8$, of these domain boundaries of the intermediate
nonperturbative infrared QCD, and found that the two scales are correlated,
with a correlation factor $Q_{c}(Y_{2})/Q_{c}(Y_{1})$ that rises to a peak at
$N_{f} = 2$ from $N_{f} = 0$, but falls off rapidly to zero for $4 \le N_{f}
\le 8$. We concluded firmly that dynamical chiral symmetry breaking and quark
confinement while being two distinct QCD phenomena caused by two independent
component QCD forces $Y_{1}$ and $Y_{2}$, are nevertheless closely related
phenomena of infrared nonperturbative QCD dynamics. Their correlation leads us
to a finding that quark confinement is most favored in the $N_{f} = 2$ flavor
state of QCD, but becomes rapidly less probable for $N_{f} \geq 4$, this
finding being exactly as one observes in nature.
