Matt Lander scored 20 points as Western Illinois won its third in a row, defeating Southern Utah 63-49 on Thursday night.
Tommie Tyler added 12 points and Ceola Clark 10 for the Leathernecks (12-14, 5-10 Summit League), who won just their second league game at home.
Dallin Bachynski went 7-for-10 and scored 20 points to lead the Thunderbirds (6-20, 2-13), who dropped their fifth in a row. Davis Baker grabbed a game-high 10 rebounds.
Southern Utah, which fell to 0-8 in league road games, started both halves with long droughts.
The Thunderbirds trailed 7-0 before Bachynski converted a three-point play after 7:59 had elapsed in the first half.
The Leathernecks also scored the first seven points of the second half and held Southern Utah scoreless for 4:22 until Ryan Brimley's jumper cut it to 42-25.
Western Illinois' lead peaked at 51-27 on Tyler's 3-pointer with 11:56 left.