While team owners Fred Wilpon and Saul Katz are still having trouble opening their tight pockets for high-priced free agents, that didn’t stop their development arm, Sterling Equities, from betting on a proposal that called for bringing a massive casino with gaming tables and slots, a 500-room, full-service hotel, 1.8 million square feet of retail and other amenities to the Willets Point development site in Queens.

The Southampton-based Shinnecock Indian Nation signed on to operate the ...