Washington has a sprained foot but no fracture, Calipari added.
The sophomore was injured in Kentucky's loss to Tennessee in the SEC Tournament semifinal. He was spotted in a walking boot afterward but Calipari had said he expected Washington to play Thursday.
In addition to being its leading scorer, Washington is also Kentucky's top rebounder and shot-blocker. The 20-year-old's absence will put more pressure on the backcourt duo of Tyler Herro and Keldon Johnson.
Kentucky hasn't lost its first game of the NCAA Tournament since 2008.