Lucas had career bests in points (7.5), assists (2.2) and rebounds (1.6) in a career-high 49 games with Chicago last season.
The 5-foot-11, 165-pound Lucas played overseas from 2007-10 in Italy, Spain and China after two seasons in the NBA with Houston.
Lucas is the son of John Lucas Jr., who was taken first overall by Houston in the 1976 NBA draft.
Gray averaged 3.9 points, 5.7 rebounds and 16.6 minutes over 49 games with the Raptors last season. The 27-year-old averaged 3.1 points and 4.2 rebounds for New Orleans in 2010-11.
The 7-foot, 270-pound Gray was a second-round selection of the Chicago Bulls in the 2007 NBA draft.