Fa relentlessly battered Keith Barr (17-11-1, 7 KOs) en route to a third-round knockout.
The 6-foot-5, 272-pound Fa, who went 2-2 against world titleholder Joseph Parker in the amateur ranks, methodically beat down Barr with textbook left jab-right combinations time and again.
He dropped Barr, 32, of Glenville, West Virginia, in the second round and hammered him around the ring for most of the round.
In the third round, he landed at will, connecting with about two dozen unanswered punches before a left hook to the body dropped Barr to a knee.
