Douglas, 30 played six games for Memphis in December, averaging 5.8 points, 2.7 rebounds, 2.7 assists and 17.8 minutes. He was waived Dec. 15. Douglas scored in double figures twice during his first stint with the Grizzlies.
The 6-foot-2 guard has appeared in 376 regular-season games (65 starts) during his eight-year NBA career with the New York Knicks, Houston Rockets, Sacramento Kings, Golden State Warriors, Miami Heat, New Orleans Pelicans and Memphis.
Williams, 22, appeared in 24 games with 13 starts for the Grizzlies this season. The 6-foot-7 forward averaged 5.3 points, 1.8 rebounds and 17.4 minutes.