Harkless, 24, was previously ruled out of Tuesday's game against the New Orleans Pelicans at Smoothie King Center because of knee soreness. The Blazers said Harkless has a "loose body" in his knee a doctor will look to clean up.
A timetable for his return will be given Wednesday.
Harkless has appeared in 59 games this season for Portland, averaging 6.5 points and 2.7 rebounds in 21.4 minutes. He's alternated between starting and bench roles throughout the year but had seen his play pick up before the injury. The St. John's product had scored in double figures in five of his last six games.
The Blazers' plan, at least for one night, appeared to be giving Evan Turner extended minutes. Turner played 36 minutes in the 107-103 win over the Pelicans; he'd played no more than 22 minutes in any of the previous five games.