Two years after setting an NC State record with a 27-game hitting streak in 1986, the left-handed Briley reached the majors. He smacked thirteen homers in 1989, his first full major-league season, but never again approached that total. Instead, Briley was valued most for his versatility and speed, spending most of his first five seasons platooning with Henry Cotto on a series of awful Mariners teams.
Seattle released Briley in March 1993. He signed with the expansion Florida Marlins, but was cut loose after a forgettable season in which his average lingered below the Mendoza line.