The primary reason why Stu changed from gin to poker was that Stu was a little too good at it. So skilled was he, that no player could stand up to him. Even the commonly called experts who were supposed to be the most favorable at gin were crushed when they competed with Mr. Ungar. One of these gin rummy player was Harry Stein, nicknamed, "Yonkie". Mr. Stein suffered such a humiliating blow at the hands of Stu Ungar that he evidently quit participating in it as a pro and never resurfaced at a gin rummy tournament.
Certainly, with a honor like that it wasn’t very long before people became shy of wagering against stu. He could not find any games and in his boredom he started doing something no one had performed before. He began offering starting handicaps to potential adversaries with the wish that they might play opposed to him if they thought they had an advantage. He at will played from a bad arrangement and one story has it that he even competed against a constant absconder. Mid contest, he received advice that the cheater was at it again but stu stated that he was aware of the chicanery and he would still win, which he did, of course.
The same problem followed Stu Ungar to Las Vegas. He won so frequently that the casinos began requesting that he not to bet on their casinos anymore. The basis for it was that other poker room customers refused to sit at the table if Stu was seated.
Stu Ungar is remembered more for his accomplishments in holdem poker but he himself always maintained that he was a whole lot more accomplished at gin rummy.
He defeated Doyle Brunson in the World Series of Poker in 1980 and became the youngest world champion. Due to his looks that made him seem far younger than he really was, he got the nickname, "The Kid".