Washington, Kentucky's leading scorer and rebounder in the regular season, didn't start but played 26 minutes and scored 16 points as Kentucky, the No. 2 seed in the Midwest Regional, outlasted Houston 62-58.
"It kind of started hurting in the second half, but I just suffered through it,'' said Washington, who added he took painkillers before the game. "I'm definitely going back to get some treatment after this and get a good night's sleep."
The Wildcats will play 5-seed Auburn on Sunday for the right to advance to the Final Four.
"It's good to have PJ back,'' Kentucky coach John Calipari said. "We don't win the game today without him. What he did and the presence he adds to the game and his ability to pass and do different things and you're not going to [overpower] him. You're not going to muscle him. You're not going to push him around. It's not going to happen.''
Washington sprained his foot in the SEC tournament and didn't play in the Wildcats' NCAA tournament victories over Abilene Christian and Wofford. He wore a cast this week and resumed practicing Thursday but wasn't a lock to play until shortly before game time against Houston.
"How we got through last weekend without him, I have no idea,'' Calipari said. "If you take the best player off any team in the NCAA tournament, you're not going to be the same. We just happened to survive.''