Funny, since Usher happens to be a minority owner of the Cleveland Cavs ... and it's almost like Nick Young and company were trying to send a friendly message -- "We're coming!"

While passing around the trophy, Swaggy P took over music duties -- and busted out Usher's greatest slow jams hits ... from "Nice & Slow" to "U Remind Me" and even "Burn."

Most of the players were diggin' it -- singing along and even dancing.