Aluko, a summer arrival from Rangers, is City's top scorer this season with eight goals and played in Saturday's 3-1 defeat against Sheffield Wednesday at the KC Stadium.
However, the 23-year-old has been nursing an Achilles problem for several weeks and was not risked for Tuesday night's 2-1 FA Cup replay extra-time win over Leyton Orient.
After the Orient victory, Bruce confirmed the extent of Aluko's problem, which is likely to sideline him until the final week of February.
"Sone Aluko looks to have a slight tear to his Achilles and could be out for around six weeks," Bruce said in comments reported by Hull's official Twitter feed, @hullcityteam.
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- Sone Aluko