Aldridge, an All-Star forward who averages a team-best 23.5 points and 10.3 rebounds, will miss his second straight game with a left foot sprain. Afflalo, who has a strained right shoulder, also will miss his second straight game.
Afflalo has started 19 of 25 games since coming over in a February trade with Denver. He is averaging 10.6 points with the Trail Blazers.
Monday night's game is important for Oklahoma City. The Thunder began the day tied with New Orleans for the No. 8 spot in the Western Conference, but the Pelicans hold the tiebreaker with two games remaining.
Portland is locked into the No. 4 seed in the West.