Northern Illinois has to hope Western Michigan beats Toledo on Friday, which would create a tie among those three, to advance to the title game against East Division champion Bowling Green.
The Huskies beat both teams and would win a three-way tiebreaker.
Sprague hit Jordan Reid for a 28-yard touchdown to opening the scoring and Windham threw 5 yards to Keith Heizman in the second quarter to make it 17-7.
NIU got within 20-14 with the only points in the third quarter before Yazdani hit two 25-yard field goals.