Wallace was helped off the floor with just over 5 minutes left
in Saturday's 100-97 victory after Haslem's head hit his knee.
Wallace, who had 15 rebounds, is listed as day to day.
The Bulls start a seven-game trip Wednesday, when they visit the
Los Angeles Clippers.
"We're very happy that Ben's injury doesn't appear to be
serious," trainer Fred Tedeschi said in a statement. "We hope to
know more, in regard to his return to the court, in the next couple
Wallace is averaging 6.5 points and 10.1 rebounds in his first
season with the Bulls.