Standard de Liege could well end the week in third place following a surprising 1-2 defeat by Charleroi Sport Club on Friday.
Standard began the day in shared first place with Club Brugge, who did have a slightly better goal record.
Yajour put Charleroi in the lead on 33 minutes but Nicaise equalised shortly before the interval. Charleroi would take the points though, with a dramatic 89th-minute winner from Habibou.
Standard risk being surpassed by Anderlecht, who face Germinal Beerschot on Sunday. Leaders Brugge host KV Kortrijk a day earlier.