14. A, B, C, and D are competing in a table tennis tournament, where every two individuals play one match against each other. As a result, A defeated D, and A, B, and C have the same number of wins. How many matches did D win?
14. Treat people as points, and get a directed graph $G$, from the conditions we know: $d^{+}($甲 $) \geqslant 1, d^{+}(\mathrm{J}) \leqslant 2, d^{+}$(甲) $=d^{+}($乙 $)=d^{+}$(丙).
(1) If $d^{+}$(甲) $=1$, then $d^{+}$(甲) $+d^{+}$(乙 $)+d^{+}$(丙) $+d^{+}$(丁) $=1+1+1+$ $d^{+}(\mathrm{J})=C_{4}{ }^{2}=6$, so $d^{+}(\mathrm{J})=3$, which contradicts $d^{+}(\mathrm{J}) \leqslant 2$.
(2) If $d^{+}$(甲) $=3$, then $d^{+}$(甲) $+d^{+}$(乙 $)+d^{+}$(丙) $=9>6=d^{+}$(甲) $+d^{+}$
(乙) $+d^{+}$(丙 $)+d^{+}$(丁), thus contradicting $d^{+}(丁) \geqslant 0$.
Therefore, it can only be that $d^{+}$(甲 $)=2$, hence $d^{+}(丁)=0$.